Immunopathology Lecture 1

OBJECTIVES

Differentiate between the concepts of “Innate” and “Adaptive” immunity

Recognize and understand the basic roles of cells of immune system (lymphocytes, macrophages, dendritic cells, NK cells )

Understand the roles of the cytokines in immunity Differentiate & give examples of the four (4) different types of

hypersensitivity reactions Know the common features of autoimmune diseases, & the usual four (4)

main features (etiology, pathogenesis , morphology, & clinical expression) of Systemic Lupus Erythematosus, Rheumatoid Arthritis, Sjögrens, Systemic Sclerosis (Scleroderma), Mixed Connective Tissue Disease, and “Poly arteritis Nodosa -

Differentiate between Primary (Genetic) & Secondary (Acquired) Immunodeficiencies

Understand the usual four (4) main features of AIDS, i.e., etiology, pathogenesis, morphology, clinical expression

Understand the usual four (4) main features of Amyloidosis

Introduction:

• Immunity = protection against infections,

• immune system : is the collection of cells and molecules that are responsible for defending us against the countless pathogenic microbes in our environment.

• Defense against microbes consists of two types of reactions : \ - Innate immunity & - Adaptive immunity

Innate immunity (AKA : natural, or native, immunity) :

is mediated by cells and proteins that are always present and poised

to fight against microbes and are called into action immediately in response to infection .

The major components of innate immunity are: • Epithelial barriers : skin, gastrointestinal tract, & respiratory tract, which prevent microbe entry 2- Phagocytic leukocytes (neutrophils & macrophages); 3- Natural killer (NK )cell; a specialized cell type 4- Complement system : circulating plasma proteins

Adaptive immunity (Also Known As Acquired or Specific immunity, Immune system, & Immune response .)

• Adaptive immunity is normally silent and responds (or "adapts )"to the presence of infectious microbes by becoming active, expanding, & generating potent mechanisms for neutralizing and eliminating the microbes

• . The components of the adaptive immune system are lymphocytes and their products . CELLULAR, i.e., direct cellular reactions to antigens

• HUMORAL, i.e., antibodies . .

CELLS of the IMMUNE SYSTEM

• LYMPHOCYTES, T

• LYMPHOCYTES, B

• PLASMA CELLS (MODIFIED B CELLS)

• MACROPHAGES, “HISTIOCYTES”, (APCs, i.e., Antigen Presenting Cells)

• “DENDRITIC” CELLS (APCs, i.e., Antigen Presenting Cells)

• NK (NATURAL KILLER) CELLS

• . T-lymphocytes (thymus derived ) : • express antigen receptors called T cell receptors (TCRs) that recognize

peptide fragments of protein antigens that are displayed by MHC molecules on the surface of antigen-presenting cells.

• constitute 60 -70 % of peripheral lymphocytes CD4 helper ,inducer 60 % of T cells. • CD8 cytotoxic ,suppressor 30 % of T cells. • CD4 :CD8 2:1 in normal healthy person

• CD4 Class II MHC. • CD8 Class I MHC. • Effector CD4 (TH1) secret IL-2 &IFN-8. (TH2 ) secret IL-4 ,IL-5 &IL-10. • Cellular immunity

2 .B- lymphocytes (Bone marrow derived ) express membrane-bound

antibodies that recognize a wide variety of antigens. • They constitute 10-20 % of peripheral lymphocytes • On antigenic stimulation B-cells differentiated to

– plasma cell – secrete immunoglobulin ( Ig ) – humoral immunity

• 5 types of Ig (IgG ,IgM ,IgA ,IgE & IgD)

4.Dendritic cells ( antigen presenting cell “APC”)

interdigitating D.C.

Langerhan’s Cell (skin).

Follicular D.C. 5.Natural killer (NK) cells

• Constitute 10-15% of peripheral blood lymphocytes

• most important source of INF-α

• kill cells that are infected by some

• microbes, or are stressed and damaged beyond repair.

• express inhibitory receptors that recognize MHC molecules that are normally expressed on healthy cells, & are thus prevented from killing normal cells

express inhibitory receptors that recognize MHC molecules that are normally expressed on healthy cells, & are thus prevented from killing normal cells

GENERAL SCHEME of CELLULAR EVENTS

• APCs (Macrophages, Dendritic Cells)

• T-Cells (Control Everything)

–CD4 “REGULATORS” (Helper)

–CD8 “EFFECTORS”

• B-Cells Plasma Cells AB’s

• NK Cells

CYTOKINES/CHEMOKINES

• CYTOKINES ( PROTEINS produced by MANY cells, but usually LYMPHOCYTES and MACROPHAGES) , have numerous roles in acute and chronic inflammation, AND immunity

Soluble mediators of the immune system 1.Cytokines that mediate natural immunity (IL-1, TNF-α, type I –IFN & IL-8 ). 2.Cytokines that regulate lymphocytes growth activation & differentiation. 3.Cytokines that activate inflammatory cells. 4.Cytokines i.e. stimulate haematopoiesis (CSF , GM-CSF.) 5.Cytokines therapy of cancer (immunotherapy). 6.Chemokines: 7. induce their effect autocrine. paracrine. endocrine.

It is the antigens responsible for the rejection of transplanted organs. • Based on their chemical structure ,tissue distribution & function . MHC gene

products fall in to 3 categories : 1. Class I MHC [HLA-A,HLA-B,HLA-C]{& all nucleated cells & platelets } • CD8 +T-cell class I MHC

2. Class II MHC [HLA-D [ DP,DQ,DR] CD4+T-cell +{APC’s,} class II MHC 3. Class III molecules [complement C2,C3&BF] they don't act as

histocompatibility (transplantation) antigen. Figure 5-4 The HLA complex and the structure of HLA molecules . A , The location of genes in the HLA complex . B , Schematic diagrams and crystal structures of class I and class II HLA molecules

• organ transplantation.

• induction & regulation of immune response especially HLA Class II .

• paternity test.

• HLA & Disease Association e.g.ankylosing spondylitis HLA-B27

Figure 5-3 Lymphocyte antigen receptors.

• The T-cell receptor (TCR) complex and other molecules involved in T-cell activation .The TCRα and TCRβ chains recognize antigen (in the form of peptide-MHC complexes expressed on antigen-presenting cells), & the linked CD3 complex initiates activating signals .CD4 and CD28 are also involved in T-cell activation( .Note that some T cells express CD8 and not CD4; these molecules serve analogous roles

Figure 5-5 Adaptive immune responses consist of sequential phases : recognition of antigen by specific lymphocytes, activation of lymphocytes (consisting of their proliferation & differentiation into effector cells), & the effector phase (elimination of antigen .) The response declines as antigen is eliminated, & most of the antigen-stimulated lymphocytes die by apoptosis . The antigen-specific cells that survive are responsible for memory . The duration of each phase may vary in different immune responses . These principles apply to humoral immunity (mediated by B lymphocytes )and cell-mediated immunity (mediated by T lymphocytes

SUMMARY

:Overview of Normal Immune Responses

• The physiologic function of the immune system is defense against infectious microbes.

• The early reaction to microbes is mediated by the mechanisms of innate immunity , which are ready to respond to microbes .

– These mechanisms include epithelial barriers, phagocytes, NK cells, and plasma proteins, ( the complement system ( .

– The reaction of innate immunity is often manifested as inflammation. SUMMARY :Overview of Normal Immune Responses ( cont’d )

• The defense reactions of adaptive immunity develop slowly, but are more potent & specialized.

• Microbes & other foreign antigens are captured by dendritic cells & transported to lymph nodes, where the antigens are recognized by naïve lymphocytes.

• The lymphocytes are activated to proliferate & differentiate into effector & memory cells.

• Cell-mediated immunity is the reaction of T lymphocytes, designed to combat cell-associated microbes (e.g., phagocytosed microbes & microbes in the cytoplasm of infected cells. SUMMARY :Overview of Normal Immune Responses ( cont’d )

• Humoral immunity is mediated by antibodies & is effective against extracellular microbes (in the circulation and mucosal lumens.)

• CD4+ helper T cells help B cells to make antibodies, activate macrophages to destroy ingested microbes, & regulate all immune responses to protein antigens .

• The functions of CD4+ T cells are mediated by secreted proteins called cytokines.

• CD8+ cytotoxic T lymphocytes kill cells that express antigens in the cytoplasm that are seen as foreign (e.g .virus-infected and tumor cells.)

• Antibodies secreted by plasma cells neutralize microbes and block their infectivity, & promote the phagocytosis & destruction of pathogens .

• Antibodies also confer passive immunity to neonates .

Immunopathology Lecture 2 Immune diseases These may result from:

Excessive immune responses (hypersensitivity reactions)

Unwanted or inappropriate immunes response ( Autoimmune diseases )

Inadequate immune responses (immunodeficiency disease)

Objective:

• Differentiate & give examples of the four (4) different types of hypersensitivity reactions HYPERSENSITIVITY REACTIONS (HSR)

HSR = excessive immune responses that result from Ag that interact with humoral Ab or by cell mediated immune mechanisms & produce a severe & damaging reaction.

a. Type 1 hypersensitivity (IgE) anaphylactic type

• may be defined as a rapidly developing immunologic reaction occurring within minutes after the combination of Ag with Ab (IgE) bond to mast cells or basophils in individuals previously sensitized to the Ag .

• Example of diseases

• Local reaction – Atopic dermatitis ( acute eczema ) – Allergic rhinitis (Hay fever) often associated with • Atopic conjunctivitis • Extrinsic allergic asthma • Food allergy

• Systemic reaction:

– Systemic anaphylaxis e,g., Penicillin, bee venom

Sequence of events in immediate (type 1 )hypersensitivity - introduction of an allergen, - which stimulates TH2 responses & IgE production . - IgE binds to Fc receptors (FcεRI )on mast cells, -& exposure to the allergen -activates the mast cells to secrete the mediators that are responsible for the pathologic manifestations of immediate hypersensitivity. 1- Vasoactive amine released from granule stores :e,g, Histamine, 2-Newly synthesized lipid mediators e.g, Prostaglandins & Leukotrienes 3- Cytokines these are important for the late phase e.g. TNF & Chemokines for leukocytes ,IL-4 & IL-5 Role of Mast Cells & Basophils

• Mast cells are located in the connective tissue of virtually all organs; high concentration in lungs, skin, GI and genital tract.

• Basophils circulate in blood and migrate into tissues.

• Each cell can bind 10,000-40,000 IgE.

• Cytoplasmic granules contain physiologically active cytokines, histamine, etc.

• Cells degranulate when stimulated by allergen. Immediate hypersensitivity

• A , Kinetics of the immediate and late-phase reactions .The immediate vascular and smooth muscle reaction to allergen develops within minutes after challenge (allergen exposure in a previously sensitized individual), and the late-phase reaction develops 2 to 24 hours later .

• B - The immediate reaction is characterized by vasodilation, congestion, and edema,

• C - the late-phase reaction is characterized by an inflammatory infiltrate rich in eosinophils, neutrophils, and T cells . Diagnosis of Allergy

• Important to determine if a person is experiencing allergy or infection

• Skin testing Treatment and Prevention X General methods include:

• Avoiding allergen

• Use drugs that block the action of the lymphocytes, mast cells, chemical mediators – antihistamines.

• Desensitization therapy – injected allergens may stimulate the formation of high-levels of allergen-specific IgG that act to block IgE; mast cells don’t degranulate

Antibody-Mediated Diseases (Type II Hypersensitivity)

• Antibody-mediated (type II )hypersensitivity disorders are caused by antibodies directed against target antigens on the surface of cells or other tissue components .

• The antigens may be normal molecules intrinsic to cell membranes or extracellular matrix, or they may be adsorbed exogenous antigens (e.g., a drug metabolite .)

• Antibodies cause disease by targeting cells for phagocytosis, by activating the complement system, and by interfering with normal cellular functions

• The antibodies that are responsible are typically high-affinity antibodies capable of activating complement and binding to the Fc receptors of phagocytes

TYPE II DISEASES

• Autoimmune Hemolytic Anemia, AHA

• Idiopathic Thrombocytopenic Purpura, ITP

• Goodpasture Syndrome (Nephritis and Lung hemorrhage)

• Rheumatic Fever

• Myasthenia Gravis

• Graves Disease

• Pernicious Anemia, PA

Antibody-Mediated Diseases (Type II Hypersensitivity • Opsonization and phagocytosis . ( ADCC) When circulating cells, such as

erythrocytes or platelets, are coated (opsonized )with autoantibodies, with or without complement proteins, the cells become targets for phagocytosis by neutrophils and macrophages .

• These phagocytes express receptors for the Fc tails of IgG antibodies and for breakdown products of the C3 complement protein ( C3b), and use these receptors to bind and ingest opsonized particles .Opsonized cells are usually eliminated in the spleen, and this is why splenectomy is of some benefit in autoimmune thrombocytopenia and hemolytic anemia . Antibody-Mediated Diseases (Type II Hypersensitivity

• Inflammation . Antibodies bound to cellular or tissue antigens activate the complement system by the "classical "pathway

• Products of complement activation recruit neutrophils and monocytes, triggering inflammation in tissues, opsonize cells for phagocytosis, and lyse cells, especially erythrocytes .

• Leukocytes may also be activated by engagement of Fc receptors, which recognize the bound antibodies Antibody-Mediated Diseases (Type II HSR)

• Antibody-mediated cellular dysfunction • . Antibodies can stimulate cell function inappropriately .In Graves' disease,

antibodies against the thyroid-stimulating hormone receptor stimulate thyroid epithelial cells to secrete thyroid hormones, resulting in hyperthyroidism

• In some cases, antibodies directed against cell surface receptors impair or dysregulate cellular function without causing cell injury or inflammation .

• In myasthenia gravis, antibodies against acetylcholine receptors in the motor end plates of skeletal muscles inhibit neuromuscular transmission, with resultant muscle weakness.

• Antibodies against hormones and other essential proteins can neutralize and block the actions of these molecules, causing functional derangements .

c. Type III hypersensitivity (immune complex mediated )

• Systemic (serum sickness)

• Local (arthus reaction) the pathogenesis of systemic immune complex : formation of ag-ab complexes in the circulation. deposition of immune complexes in various tissues through out the body.

Thus initiating an inflammatory reactions in various tissues through the body.

Systemic Immune Complex Disease The pathogenesis of systemic immune complex disease can be divided into three phases( :1 )formation of antigen-antibody complexes in the circulation and (2 )deposition of the immune complexes in various tissues, thus initiating (3 )an inflammatory reaction in various sites throughout the body Local Immune Complex Disease ( Arthus reaction) The pathogenesis of Local immune complex disease can be divided into 4 phases: (1 ) Deposition of the immune complexes in vascular wall (2) Complement activation (3) Chemotactic attraction & activation of PMNs )4 )an inflammatory reaction in various sites throughout the body Morphology of IC disease is dominated by acute necrotizing vasculitis (Fibrinoid necrosis ) .The wall of the artery shows a circumferential bright pink area of necrosis with protein deposition and inflammation d. Type 4 hypersensitivity (cell-mediated)

• A. delayed –type hypersensitivity (DTH) e.g. tuberculin reaction

• Granuloma is special type of DTH occurring in the setting of persistent &/or non degradable Ag

• The initial perivascular CD4+T cell infiltration is progressively replaced by macrophages over a period of 2-3 weeks leading to epitheliod cell which covert to giant cells.

A. delayed –type hypersensitivity (DTH) e.g. tuberculin reaction, Contact dermatitis B. T-cell-mediated cytotoxcity : here sensitized CD8-T cell kill antigen bearing target cells : 1. graft rejection 2.virus infection 3.tumor immunity C. T-cell-mediated cytotoxcity by NK cell

Lecture 3

Transplantation rejection, Autoimmune Diseases

• It is a complex immunologic phenomenon involving both cell & antibody mediated hypersensitivity responses of the host directed against histocompatibility molecules on the donor allograft

Indirect recognition • Host CD4+Tcells recognize donor HLA after they are processed &

presented by host own APCs activate DTH pathway (type IV hypersensitivity )

Direct recognition The host respond to donor HLA expressed directly on donor cells . • CD8+Tcell CTL lyses targets in grafted tissue endothelial cell

death thrombosis ischemia rejection .

Direct recognition The host respond to donor HLA expressed directly on donor cells

Indirect recognition Host CD4+Tcells recognize donor HLA after they are processed & presented by host own APCs activate DTH pathway (type IV HSR )

Patterns of transplant rejection

• Hyperacute rejection- due to preformed host antibodies reacting with HLA – Ag. in the donar organ,

• Acute rejection – a) acute vascular rejection associated with necrosis of vessels in the graft. b) acute cellular rejection- infiltration of the graft tissue by CD+ T-lymphocytes. 3. Chronic rejection – slow progressive destruction of graft structure &

function mainly as a vascular occlusion + cellular infiltration Hyperacute rejection:

Occurs within minutes to a few hours after transplantation in a presensitized host just after the vascular anastomosis is completed.

kidney rapidly becomes cyanotic, mottled, & flaccid and may excrete only a few drops of bloody fluid .

The histology is characterized by widespread acute arteritis & arteriolitis, vessel thrombosis, and ischemic necrosis, all resulting from the binding of preformed antibodies to graft endothelium .

Acute rejection Acute rejection may occur within days to weeks of transplantation in a non-

immunosuppressed host or may appear months or even years later, even in the presence of adequate immunosuppression .

Acute rejection is caused by both cellular and humoral immune mechanisms,

and in any one patient one or the other may predominate . Histologically, – cellular rejection is marked by an interstitial mononuclear cell infiltrate with

associated edema and parenchymal injury, – whereas humoral rejection is associated with vasculitis .

Acute rejection A- Acute cellular rejection B- Acute humoral rejection ( vascular rejection)

Chronic rejection • Chronic rejection . Dominated by arteriosclerosis, this type is probably caused

by T-cell reaction & secretion of cytokines that induce proliferation of vascular smooth muscle cells, associated with parenchymal fibrosis .

Autoimmune Diseases • These are diseases caused by an immune reaction against self-Ag. ( i.e.

failure of self tolerance )

• * They may involve – single organ – multisystemic.

• *Affecting mainly female.

Self- Tolerance

• Self-Tolerance refers to a lack of immune responsiveness to the individual own tissue antigens

• The mechanisms of self tolerance are: – Clonal deletion – Clonal anergy – peripheral suppression by suppressor T-lymphocyte

Figure 5-18 The principal mechanisms of central & peripheral self-tolerance in CD4+ T cells .

1- Clonal deletion:

• loss or deletion of self reactive clones of T or B-lymphocytes or both during their maturation

• Many self antigens expressed in the thymus in associated with MHC, the developing T cells that express high affinity receptors for such self antigens are deleted by apoptosis

• Self reactive B-cells also affected but to less extend than T cells

2- Clonal anergy:

• Those cells that escape clonal deletion in thymus, become inactive outside the thymus by clonal anergy

• It is prolonged or irreversible functional inactivation of lymphocytes induced by failure of expression of co-stimulators (e.g., B7-1 & B7-2) in the APC & parenchymal tissue, so negative signal is delivered make the cell anergic

• Affect both T & B cells

• It is the major mechanism for B cell tolerance

3- Peripheral suppression by T cells:

• presence of CD8 suppressor T cells make this mechanism

• they inactivate both helper T cells & B cells

• they act through secretion of inhibitory cytokines such as IL-10

Mechanisms of autoimmune disease A) Loss of self – tolerance B) Genetic factors in autimmunity

A) Loss of self - tolerance

1- Bypass of helper T- cell tolerance: by • A /modification of molecule: if self antigen is modified as due to drugs or

microorganisms, this recognized by T cells as a foreign antigen so cooperate with B cells leading to formation of autoantibodies as in autoimmune hemolytic anemia

• B /Expressions of costimulatory molecules: as in infection which can activate macrophages to express costimulatory molecules and present self antigens

2- Molecular mimicry:

• Some infectious agent share epitopes with self antigens so cross reaction with self antigen is result as in rheumatic heart disease

3- Polyclonal lymphocyte activation:

• Some of autoreactive lymphocytes that were not deleted during development may become stimulated by :

– antigen independent mechanisms as in endotoxins of bacteria induced polyclonal antibody against self antigens

4- Imbalance of suppressor-Helper T-cell function:

• loss of suppressor T cell function or

• excessive helper T cell function result in B cell activation 5- Emergence of sequestered antigens:

• Some antigen are anatomically segregated from the developing immune system special clonal deletion or anergy fails to occur, if they release into circulation they induced an immune response e.g., ocular antigens B) Genetic factors in autoimmunity

• They play significant role in the predisposition to autoimmune diseases.

• The evidence for that are: 1-Familial clustering of several human autoimmune diseases e.g., SLE,

autoimmune hemolytic anemia, & autoimmune thyroiditis 2-Linkage of several autoimmune diseases with HLA especially class II 3-Induction of autoimmune diseases in transgenic rats by introduce certain

human HLA e.g., HLA-B27 C) Microbial agents in autoimmunity

• Included bacteria, mycoplasmas, & viruses

• mechanisms are: 1-association of microbial antigens & autoantigens forming new immunogenic

units & by pass T-cell tolerance 2-Induction of nonspecific polyclonal B-cell mitogens & formation of

Autoantibodies 3-loss of suppressor T cell function 4-Cross reaction with self antigens

• Why does some autoimmune disease affecting single organ while other are systemic?

* They depend on the nature of Ag: (1) If Ag restricted in its expression to single organ e.g., Grave’s disease the

autoimmune disease will be limited to the cells of that organ only. (2) If more organs express the same Ag, so more wide spread diseases occur.

AUTO-IMMUNE DISEASES

• Failure of SELF RECOGNITION

• Failure of SELF TOLERANCE

• TOLERANCE

– CENTRAL (Death of self reactive lymphocytes)

– PERIPHERAL (anergy, suppression by T-cells, deletion by apoptosis, sequestration (Ag masking))

• STRONG GENETIC PREDISPOSITION

• OFTEN RELATED TO OTHER AUTOIMMUNE DISEASES

• OFTEN TRIGGERED BY INFECTIONS CLASSIC AUTOIMMUNE DISEASES (SYSTEMIC)

• LUPUS (SLE) Systemic Lupus Erythematosus

• RHEUMATOID ARTHRITIS

• SJÖGREN SYNDROME

• SYSTEMIC SCLEROSIS (scleroderma)

• “collagen” diseases (term no longer used) LUPUS (SLE)

• Etiology: Antibodies (ABs) directed against the patient’s own DNA, HISTONES, NON-histone RNA, and NUCLEOLUS

• Pathogenesis: Progressive DEPOSITION and INFLAMMATION to immune deposits, in skin, joints, kidneys, vessels, heart, CNS

• Morphology: “Butterfly” rash, skin deposits, glomerolunephritis (NOT discoid)

• Clinical expression: Progressive renal and vascular disease, POSITIVE A.N.A.

Systemic Lupus Erythromatosus

Definition: -

• multisystem disease of autoimmune origin, acute or gradual in onset, chronic, remitting & relapsing febrile illness characterized principally by injury to the skin, joint, kidney & serosal membranes.

• * Female: male ratio 9:1.

• * Age group 20-40 years. Systemic Lupus Erythromatosus

* Four out of 11 clinical or laboratory criteria must be present for diagnosis of SLE: • ( 1 )Malar rash. • (2) Discoid rash. • (3) Photosensitivity. • (4) Oral ulcers. • (5) Arthritis. • (6) Serositis. • (7) Renal disorders. • (8) Neurological disorders (seizures, psychosis). • (9) Hematological disorders (cytopenia, hemolytic anemia). • (10) Immunological disorder (Ab to DNA or anti-Sm, antiphospholipid Ab). • (11) Antinuclear Ab.

Etiology & pathogenesis 1- Immunologic Factors:

• Autoantibodies result from hyperactivity of B cell which occur as a result of A/ intrinsic defect in B cells B/ excessive stimulation by helper T cells C/ Defect in suppressor T cell function

2- Genetic factors: High rate of concordance (30%) in monozygotic twins

• Family members have an increased risk of developing SLE & even may show autoantibodies

• Association between SLE & HLA-DQ locus

• 6 % of patients have inherited deficiencies of complement components

3- Non genetic factors:

• Occurrence of SLE in patients received certain drugs as procainamide & hydralazine

• Sex hormones esp. estrogen

• Ultraviolet light exposure • ANA are directed against several nuclear Antigens & categorized into: (1) Ab against DNA. (2) Ab to histones. (3) Ab to histone proteins bound to RNA (smith Ag, SS-A, SS-D). (4) Ab to nucleolar Ag.

Characteristic morphological finding in SLE: *Skin: granular deposition of immune complex along the epidermal-dermal

basement membrane producing maculopapular eruption over the malar eminencies & bridge of the nose producing butterfly pattern

*Appearance of LE bodies (hemotoxylin bodies), nuclei of damaged cells react

with ANAs loss their chromatin pattern and become homogenous. *LE bodies in vitro engulfed by macrophages or neutrophils forming LE cells *LE cells positive in 70 % of patients *Acute necrotizing vasculitis affecting small arteries & arterioles especially of skin & muscles

Kidney: deposition of immune complex in glomerular blood vessels & tubules.

, in a "wire loops"called -Glomerulus with thickened pink capillary loops, the sopatient with lupus nephritis

**joint involvement: swelling & inflammation * Heart: immune complex deposition on the value especially mitral value. • *Pericarditis (most common). • * Endocarditis (Libman-Sacks). • * Non specific myocarditis • * Accelerated coronary atherosclerosis

* spleen: marked perivascular fibrosis giving onion-skin lesion

MORE SYSTEMIC AUTOIMMUNE DISEASES

• RHEUMATOID ARTHRITIS

• SJÖGREN SYNDROME

• SCLERODERMA (SYSTEMIC SCLEROSIS)

Rheumatoid Arthritis • RA is a chronic inflammatory disease that affects mainly the joints, especially

small joints, but can affect multiple tissues. • The disease is caused by an autoimmune response against an unknown self

antigen(s), which leads to T-cell reactions in the joint with production of cytokines that activate phagocytes that damage tissues and stimulate proliferation of synovial cells (synovitis .)

• The cytokine TNF plays a central role, & antagonists against TNF are of great benefit .Antibodies may also contribute to the disease .

Figure 5-25 Model for the pathogenesis of rheumatoid arthritis .CD4+ T cells reacting against an unknown arthritogenic antigen are believed to stimulate

autoantibody production and to activate macrophages and other cells in the joint synovium .PGE 2 , prostaglandin E 2 .

Figure 5-23 Rheumatoid arthritis .

• A , A joint lesion .B , Low magnification reveals marked synovial hypertrophy with formation of villi .C , At higher magnification, dense lymphoid aggregates are seen in the synovium.

Sjögren Syndrome Sjögren syndrome is an inflammatory disease that affects primarily the salivary

and lacrimal glands, causing dryness of the mouth and eyes. The disease is believed to be caused by an autoimmune T-cell reaction against

an unknown self antigen(s )expressed in these glands, or immune reactions against the antigens of a virus that infects the tissues .

Systemic Sclerosis

• Systemic sclerosis (commonly called scleroderma ( • is characterized by progressive fibrosis involving the skin, gastrointestinal

tract, and other tissues. • Fibrosis may be the result of activation of fibroblasts by cytokines produced

by T cells, but what triggers T-cell responses is unknown.

• Endothelial injury and microvascular disease are commonly present in the lesions of systemic sclerosis, perhaps causing chronic ischemia, but the pathogenesis of vascular injury is not known .

MORE AUTOIMMUNE DISEASES (LOCAL) • HASHIMOTO THYROIDITIS • AUTOIMMUNE HEMOLYTIC ANEMIA • MULTIPLE SCLEROSIS • AUTOIMMUNE ORCHITIS • GOODPASTURE SYNDROME • AUTOIMMUNE THROMBOCYTOPENIA (ITP) • “PERNICIOUS” ANEMIA • INSULIN DEPENDENT DIABETES MELLITUS (I) • MYASTHENIA GRAVIS • GRAVES DISEASE

Immunopathology Lecture 4 immune deficiency diseases

Primary immune deficiency diseases. Lymphocyte development and sites of block in primary immune deficiency

diseases .The affected genes are indicated in parentheses for some of the disorders . ADA =) adenosine deaminase;) CD40L,= (CD40 ligand (( also known as CD154); CVID=common variable immunodeficiency; SCID,=severe combined immunodeficiency Immunodeficiency syndrome

– Primary Immunodeficiency: -( Rare ) – * Early onset, usually between 6 months & 2 years of age – * Recurrent infections – * Classification * B-cell deficiencies: - 1-X-linked agammaglobulinemia of Bruton 2-Common variable immunodeficiency

3-Isolated IGA deficiency

Primary Immunodeficiency * T-cell deficiencies: - 1-Hyper IGM syndrome 2-DiGeorge syndrome * Severe combined immunodeficiency

– X-linked Agammaglobulinaemia of Bruton

– Absent or markedly decreased concentration of all classes of Ig

– * Affecting boys (X-linked disease)

– * Symptoms appear after 6 months of age

– * Typically there is increase incidence of otitis media, skin & respiratory infections caused by

H. influenzae, S. pneumoniae, or S. aureus

Isolated IgA immunodeficiency:

• *Most common type accounts for 1/600 individuals

• * Either familial or acquired (in association with toxoplasmosis & measles)

• * Many of these men & women are asymptomatic

• * Increase incidence of respiratory, GIT & urogenital tract infections

• * Increase incidence of autoimmune diseases esp. SLE & rheumatoid arthritis – * Defect in differentiation of IgA B-cells

DiGeorge syndrome (Thymic hypoplasia)

– *T-cell deficiency due to the failure of development of thymus

– * No cell-mediate response

• * Part of CATCH 22 syndrome (Cardiac abnormality, T-cell deficiency, cleft palate, hypocalcemia)

• due to deletion of chromosome 22 Secondary IDs: These states arising as a complication of

• Chronic infection ,

• old age,

• Chronic malnutrition,

• Wide spread malignancy

• Chronic renal failure

• Side effects of immune suppression – ,irradiation , – or chemotherapy for cancer or other autoimmune diseases .

• ( Modern plague)

• it is a retroviral disease caused by HIV & characterized by immunsuppression leading to : 1.Opportunistic infections. 2.Secondary neoplasms . 3.Neurologic manifestations. Acquired immunodeficiency syndrome

AIDS is a retroviral (RNA virus) disease characterized by: - • 1-Profound immunosuppression that leads to opportunistic infections • 2- Secondary neoplasms • 3- Neurologic manifestations

Despite dramatic improvements in drug therapy, the true mortality rate is likely to approach 100 %

• In United states, AIDS is the leading cause of death in men between 25-44 year of age & third leading cause of death in women Epidemiology

• *First described in United States

• * United States has the majority of the reported cases

• * Infection in Asia & Africa now is large & expanding

• * Adults at risk for developing AIDS are: - • 1-Homosexual men constitute by far the largest group, accounting for 57

% of reported cases • 2-Intravenous drug abusers compose the next largest group accounting

about 25 % • 3-Hemophiliacs esp.. before 1985, make up 0.8 % of all cases

Epidemiology: - • 4-Recipients of blood & blood components who are not hemophiliac,

account for 1.2 % of cases • 5-Heterosexual contacts constitute 10 % of all cases • 6-Approximately 6 % of cases, the risk factors can’t be determined – 7- Newborn of infected mothers

• Close to 2 % of all AIDS cases occur in pediatric population, more than 90 % result from transmission of virus from infected mother to her baby. The remaining 10 % are hemophiliacs or received blood & blood products before 1985 Etiology: -

• *HIV is human retrovirus belonging to the lentivirus family • * 2 genetically different but related forms of HIV called HIV-1 & HIV-2 • * HIV-1 is most common type associated with AIDS in U.S, Europe & central

Africa • * P24 (major caspid protein) is the most readily detected viral Ag & target for

Ab that is used for the diagnosis of AIDS • * gp120 & gp41 are viral envelope which are critical for infection • *HIV-1 subdivided into; M & T • M form is most common form worldwide

• Pathogenesis: *2 major targets of HIV:

– A-Immune system – B-CNS A) Immunopathogensis of HIV disease: *Profound immunosuppression primary affecting cell-mediate immunity • * Severe loss of CD4 T-cells & impairment in the function of surviving helper T cell • * Macrophage & dendritic cells are also target of HIV infection • * For infection, binding of the virus to CD4 is not sufficient, therefore HIV

gp120 must also bind to co-receptor (CCR5 & CXCR4) for entry into the cells Figure 5-31 Molecular basis of HIV entry into host cells .Interactions with CD4 and a chemokine receptor "(coreceptor).

Pathogenesis of HIV infection Figure 5-33 Mechanisms of CD4 cell loss in HIV infection .Some of the principal known and postulated mechanisms of T-cell depletion after HIV infection are shown A) Immunopathogensis of HIV disease: HIV strains can be classified into 2 groups on the basis of their ability to infect

macrophage & CD4 T-cell – M-tropic which can infect both monocytes / macrophages & freshly

isolated peripheral T-cell – T-tropic which infect only T-cell

• * M-tropic strain use CCR5 receptor, whereas * T-tropic strain bind to the CXCR4 receptor which only present in T-cell

B) Pathogenesis of CNS involvement: - • *Nervous system is a major target of HIV infection • * Macrophages & micoglial cells are the predominant cell type infected with

HIV • * Infection transmitted to CNS through monocytes & are almost exclusively of

M-tropic type • * HIV does not infect Neurons • * Injury to the nervous system occurs indirectly by viral products & soluble

factors produced by macrophage / microglial cells e.g., IL1, TNF & IL6 Natural history of HIV infection:

*3 phases can be recognized -Early acute phase -Middle chronic phase -Final crisis phase

Natural history of HIV infection: .1-Early acute phase: - – * Represent the initial response of immunocompetent adult to HIV

• Clinically is associated with self limited acute illness that develop in 50-70 % of HIV infected patients such as rash, cervical lymph-adenopathy, diarrhea & vomiting which persist for 3-6 weeks Natural history of HIV infection

2-Middle chronic phase: - There is continued HIV replication predominantly in lymphoid tissue

– * Patient are either asymptomatic or develop persistent generalized lymphadenopathy

– * Many patients have minor opportunistic infection such as thrush or herpes zoster

Natural history of HIV infection

.3-Final crisis phase: - * Characterized by break down of host defense * Dramatic increase in plasma virus & clinical disease * Patients present with a long standing fever (> 1 month), fatigue, weight loss &

diarrhea * CD4 cell count is reduced below 500 cell / ml * Serious opportunistic infection, secondary neoplasm or clinical neurological

diseases, these called AIDS defining conditions Opportunistic infections: -

1 )Pneumonia caused by pneumocystis carinii, about 50 % of AIDS patients develop this infection

2) Candida albicans infections of mouth, esophagus, vagina & lungs 3) cytomegalovirus enteritis & pneumonia & retinitis 4) Atypical mycobacterial infection (esp. M. avium-intracellulare) of G.I.T 5) Herpes simplex infection of mucocutanous areas

Most Common Neoplasms associated with AIDS

1)Kaposi Sarcoma: -

• * Vascular tumor

• * Most common tumor in AIDS patients 2)Non-Hodgkin lymphoma: -

• * 120 times more risk in AIDS patients than in general population Most Common Neoplasms associated with AIDS:

3)Carcinoma of uterine cervix 4)Squamous cell carcinoma of the skin 5) Hodgkin disease

Pathogenesis : The major target of HIV infection are:

Immune system CNS

THE MULTIPLE EFFECTS OF CD4+CELL AFTER HIV INFECTION:

II. pathogenesis of CNS involvement:

• Lecture 5 : Amyloidosis

OBJECTIVES • Definition • Mechanism of formation • Characteristics common to all amyloid subtypes • Classification • Clinical Importance/Symptoms • Diagnosis and Treatment

Definition Amyloidosis is a clinical disorder resulting from by extracellular deposition of

insoluble abnormal fibrillar proteins ( Amyloid) which lead to tissue damage functional impairment ِ Abnormal Protein metabolism ( hereditary or acquired ) Insoluble fibrilar

protein ( β- pleated fibrils)Excellular depositionimpairment of affected organs A ) Congo red stainCongo red stain, which under ordinary light imparts a pink or red color to amyloid deposits B) Under polarized light, the Congo red -stained amyloid shows a green birefringence (Fig. 5-35). Structure of amyloid . A, Schematic diagram of an amyloid fiber wound around one another with regularly spaced binding of the Congo red dye. B, Congo red staining shows an apple-green birefringence under polarized light, a diagnostic feature of amyloid. C, E/M amyloid fibrils linear, rigid about of 7.5-10 nm in width Amyloid is not a single substance. It is made up

– (95%) of non-branching fibril proteins, – (5%) plasma proteins, notably serum amyloid P component (SAP). – & glycoproteins

(glycoproteins give the deposits staining characteristics that were thought to resemble starch (amylose).

• more than 20 different proteins can aggregate and form fibrils with the appearance of amyloid.

• The 3 most common biochemical forms of amyloid are: AL, AA, & Aβ

• AL (Amyloid light chain):

• It is derived from plasma cells and contains immunoglobulin light chains ( most common lambda light chains, but in some cases kappa chain have

been identified )

AA (Amyloid-Associated):

• The AA protein is found in secondary amyloidosis.

• AA fibrils are derived from a larger precursor in the serum called SAA (serum-amyloid-associated) protein that is synthesized in the liver

Aβ amyloid is found in the cerebral lesion of Alzheimer disease.

• The Aβ protein is derived from a much larger Trans membrane glycoprotein, called amyloid precursor protein (APP).

• Other forms of amyloid protein :

Transthyretin (TTR) is a normal serum protein that binds and transports thyroxine and retinol.

• A mutant from of (TTR) is deposited in a group of genetically determined disorders referred as Familial Amyloid Polyneuropathies.

• Transthyretin ( when present in abnormal high concentration ) is also deposited as in (senile systemic amyloidosis)

• Because of the dominant involvement and related dysfunction of heart it was previously called senile cardiac amyloidosis which lead to restrictive cardiopathy and arrhythmias.

β2 –microglobin: • Component of the MHC class I molecules & a normal serum protein, has

been identified as the amyloid fibril subunit (Aβ2 m) in amyloidosis that complicates the course of patients on long term hemodialysis (hemodialysis-Associated A.)

• β2 –microglobin is present in high conc. in the serum of patients with renal disease and is retained in circulation because it can’t be filtered through the dialysis membranes.

• 60 - 80% of patients on long term dialysis developed amyloid deposits in the synovium, joints & tendon sheaths.

• Systemic (generalized) involving several organ systems. • Localized when deposits are limited to a single organ such as the heart,

lung, larynx skin, urinary bladder& tongue.

Systemic Amyloidosis sub classified into: 1.Primary Amyloidoisis ,when associated with some immunocyte dyscrasia. 2.Secondary Amyloidosis (reactive systemic A.) when it occurs as a

complication of underlying chronic inflammatory or tissue destructive process.

2.Secondary Amyloidosis (reactive systemic amyloidosis)

• The A. deposits in this pattern are systemic in distribution & of AA. Protein

• Previously it found in T.B., bronchiectasis& chronic osteomylitis , but with effective antimicrobial chemotherapy the importance of these conditions has diminished.

2.Secondary Amyloidosis (reactive systemic amyloidosis) cont’d • Now reactive systemic A. complicates rheumatoid arthritis, ankylosing

spondylitis & inflammatory bowel diseases ( Crohns disease & Ulcerative colitis).

• Heroine abusers who inject the drug subcutaneously also have a high occurrence rate of generalized A.A. type.

• Reactive systemic A. also occur in association with non-immunocyte derived tumors like renal cell carcinoma & Hodgkin disease.

Amyloid in this category is usually systemic in distribution & is of the AL. type It is the most common form of A. In many cases the patients have some form of plasma cell dyscrasia. Systemic A. occurs in 5-15% of patients with multiple myeloma. The malignant B cell synthesizes abnormal amounts of a single specific

immunoglobulin (monoclonal gammopathy), producing M (myeloma) protein spike on serum electrophoresis.

In addition to the synthesize of whole immunoglobulin molecules ,plasma cell may also synthesize & secret either the lambda or kappa light chain may be elaborated & found in the serum & frequently excreted in the urine ( Bence Jones proteins )

The amyloid deposits contain the same light chain protein. Almost all the patients with MM who develop Amyloidosis have Bence Jones

proteins in the serum or urine or both, but a great majority of myeloma patients who have free light chains do not develop amyloidosis.

Therefore the presence of Bence Jones proteins although necessary, is by

itself not enough to produce amyloidosis

The great majority of patients with AL amyloid do not have classic MM or any

other B - cell neoplasm. Such cases classified as Primary Amyloidosis. because their clinical features derived from the effects of amyloid deposition without any associated disease

In these cases, however , monoclonal immunoglobulin or free light chain or

both can be found in the serum or urine. Most of these patients also have modest increase in the number of plasma cells in the bone marrow which is precursors of AL-protein

These patients have an underlying B-cell dyscrasia in which production of an

abnormal protein, rather than production of tumor mass Recent studies have revealed chromosomal translocation in many of these

patients, suggesting the presence of neoplastic clones. MM if patients lived long enough can only be a matter for speculation.

Although immunocyte-associated amyloidosis cannot reliably be distinguished

from the secondary form by its organ distribution, more often it involves the heart, kidney, GIT, peripheral nerves, skin & tongue.

Macroscopically the affected organs are often enlarged, firm & have a waxy appearance.

If the deposits are sufficiently large painting the cut surface with iodine giving yellow color that is transformed to blue violet after Application of sulfuric acid.

Heart • Histologically the deposits begin in focal subendocardial accumulation &

within the myocardium between muscle fibers leading to pressure atrophy of myocardial fibers.

Spleen • Amyloidosis is limited to the splenic follicles leading to Sago spleen. • Amyloidosis limited to the wall of splenic sinuses& connective tissue

framework in the red pulp leading to Lardaceous spleen Liver • Amyloidosis appears first in the space of Disse lead to hepatoparenchymal

cells & sinusoids leading to pressure atrophy.

• G.I.T Include to types

Familial Mediterranean Fever It is autosomal recessive condition.

It is febrile disorder of unknown cause characterized by attacks of fever accompanied by inflammation of serosal surfaces, including peritoneum, pleura & synovial membranes

The amyloid fibrils proteins are made up of AA proteins, suggesting that this

form of amyloidosis is related to recurrent bouts of inflammation that characterize this disease .

The gene for familial Mediterranean fever has been cloned, and its product

is called pyrin, it has been suggested that pyrin is responsible for regulating acute inflammation, by inhibiting the function of neutrophils.

Familial Amyloidotic Polyneuropathies

It is autosomal dominant disorders.

Characterized by deposition of amyloid in the peripheral & autonomic neurons .

The fibrils are made up of mutant (ATTR). microscopic deposits of localized amyloid may be found in certain endocrine

tumors such as • Medullary carcinoma of thyroid. • Islet tumour of the pancreas. • Pheochromocytomas. • Undifferentiated carcinoma of the stomach.

The amyloidogenic proteins seems to be derived either from: • polypeptide hormones e.g. medullary ca. • OR unique proteins e.g. islet amyloid polypeptide( IAPP).

Amyloidosis results from abnormal folding of proteins which are deposited as fibrils in the extra cellular tissues & disrupt normal function.

Amyloidosis should not be considered a single disease rather it is a group of diseases having in common the deposition of similar- appearing proteins.

Figure 5-36 Pathogenesis of amyloidosis . The proposed mechanisms underlying deposition of the major forms of amyloid fibrils. The proteins that form amyloid fall in to two groups : Normal proteins that have inherent tendency to fold improperly,

associated &form fibrils, and do so when they are produced in increased amounts.

Mutant proteins that is structurally unstable & prone to misfolding & subsequent aggregation.

Normally , misfolded proteins are degraded intracellularly in proteosomes or extracellularly by macrophages

In amyloidosis, these quality control mechanisms fail. So that too much of

misfolded proteins accumulate outside cells. In the case of immunocyte dyscrasia, there is excess of immunoglobulin light

chains& amyloid can be derived by: Proteolysis of immunoglobulin light chains in vitro. Defective degradation & particularly light chains are resistant to complete

proteolysis. SAA is synthesized by liver cells under the influence of cytokines such as

IL1&6 that are produced during inflammation, thus long standing inflammation leads to elevated SAA levels leading to AA form of amyloid deposits. However increased production of SAA by itself is not sufficient for the deposition of amyloid.

There are two possible explanations for this:

SAA is normally degraded to soluble end products by the action of monocytes derived enzymes. Individuals who develop amyloidosis have an enzyme defect that results in incomplete break down of SAA thus generating insoluble AA molecules.

A genetically determined structural abnormality in SAA molecule itself renders it resistant to degradation by macrophages.

In familial amyloidosis the deposition of Transthyretin as amyloid fibrils does

not result from overproduction of Transthyretin. It has been proposed that genetically determined alteration of structure render the Tranthyretin prone to misfolding, aggregation and resistance to proteolysis.

The symptoms depend on: The magnitude of the deposits. The particular sites or organs affected. History. Clinical Examination. Investigations : Biopsy (subcutaneous, gingival, rectal, organ or abdominal omental fat). Serum and urine protein electrophoresis &immunoelectrophoresis

should be performed.

Bone marrow aspirates in case of immunocyte- associated amyloidosis after showing plasmacytosis, even in the absence of current MM.

Scintigraphy with radio labeled serum amyloid p (SAP) component is rapid and spscific test since SAP binds to amyloid deposits and reveals their presence.

The prognosis of patient with generalized amyloidosis is poor. Those with immunocyte –derived amyloidosis (not including MM) have a

median survival of two years after diagnosis. Patients with MM have a poorer prognosis. AMYLOIDOSIS • Amyloidosis is a condition associated with a number of inherited and

inflammatory disorders in which extracellular deposits of fibrillar proteins are responsible for tissue damage and functional compromise.

• These abnormal fibrils are produced by the aggregation of misfolded proteins (which are soluble in their normal folded configuration).

• The fibrillar deposits bind a wide variety of ( polysaccharides ) proteoglycans and glycosaminoglycans, including heparan sulfate and dermatan sulfate, and plasma proteins, notably serum amyloid P component (SAP).

• The presence of abundant charged sugar groups in these adsorbed proteins give the deposits staining characteristics that were thought to resemble starch (amylose). Therefore, the deposits were called amyloid,

Pathogenesis of Amyloid Deposition • Amyloidosis is fundamentally a disorder of protein misfolding. • Amyloid is not a structurally homogeneous protein, although it always has the

same morphologic appearance. • In fact, more than 20 (at last count, 23) different proteins can aggregate and

form fibrils with the appearance of amyloid. • Regardless of their derivation, all amyloid deposits are composed of

nonbranching fibrils, 7.5 to 10 nm in diameter, each formed of β-sheet polypeptide chains that are wound together (Fig. 5-35).

• The dye Congo red binds to these fibrils and produces a red-green dichroism (birefringence), which is commonly used to identify amyloid desposits in tissues.