dr shoaib raza. immune reactions against self antigens affects 1% to 2% of us population ...
TRANSCRIPT
Immune reactions against self antigens Affects 1% to 2% of US population Requirements for an autoimmune disorder:
Presence of immune reaction specific for some self-antigen or self-tissue
Evidence that the reaction is not secondary to tissue damage
Absence of another well defined cause of disease DIAGNOSIS OF EXCLUSION
Autoimmune Disorders
Clinical manifestations are varied
Organ specific disease Type 1 diabetes mellitus Multiple sclerosis
Systemic or generalized diseases Systemic lupus erythematosus
Middle of the spectrum Goodpasture’s syndrome
Autoimmune Disorders
The phenomenon of unresponsiveness to an
antigen as a result of exposure to lymphocytes to that antigen.
Self tolerance refers to lack of responsiveness to an individual’s own antigen Central tolerance Peripheral tolerance
Immunologic Tolerance
Immature self reactive T or B-Cell clones that
recognize self-antigens during their maturation in the central lymphoid organs (Thymus or Bone marrow) are killed or rendered harmless.
Central tolerance is however far from PERFECT Self reactive T or B-cells may skip the central
tolerance and enter the circulation
Central Tolerance
In the thymus
Negative selection: Self reactive T-Cells die by apoptosis AIRE protein stimulates expression of “peripheral
tissue restricted” self-antigens in the thymus Some self reactive CD4+ T-Cells in the thymus
do not die, but later on develop into regulatory cells
Central Tolerance of T-Cells
In the bone marrow:
Receptor editing: Some self-reactive B-Cells reactivate the
machinery of antigen receptor gene and begin to express new antigens receptors
If receptor editing does not occur, self-reactive B-Cells undergo apoptosis
Central Tolerance of B-Cells
Several mechanisms
Anergy Prolonged or irreversible inactivation of lymphocytes Absence of co-stimulatory signals induce apoptosis
Suppression by regulatory T-Cells Mainly developed in thymus May be developed in peripheral tissues ? immunosuppressive cytokines are released (IL-10)
Deletion by activation-induced cell death Self-reactive CD4+ T-Cells undergo apoptosis
Peripheral Tolerance
Autoimmunity arises from a combination of
Inheritance of susceptibility genes may lead to breach in self-tolerance
Environmental triggers e.g. infections and tissue damage
Mechanism of Autoimmunity
Many autoimmune diseases are:
Associated with infections Up-regulation of expression of co-stimulators on
APC Molecular mimicry (e.g. rheumatic heart disease) Polyclonal B-Cell activation (e.g. EBV infection)
Role of Infection in Autoimmune Diseases
Autoimmune diseases are PROGRESSIVE, with
relapses and remissions Clinical and pathological manifestations are
determined by nature of underlying immune response
Different autoimmune diseases show substantial clinical, serological and pathological overlap.
General Features of Autoimmune Diseases
Prototype of multisystem disease of autoimmune origin
Antinuclear antibodies (ANAs) are usually present Acute or insidious in onset Chronic, remitting and relapsing, often febrile illness
characterized principally by injury to the skin, joints, kidney and serosal membranes
Complex set of criteria for establishing the diagnosis
Systemic Lupus Erythematosus (SLE)
Exact cause is unknown Failure of the mechanisms that maintain self-
tolerance Genetic factors Immunologic factors Environmental factors
Etiology & Pathogenesis
Most of the visceral lesions are caused by Type
III Hypersensitivity reaction DNA-AntiDNA complexes are formed Immune complex nature of the disease
Autoantibodies specific for RBC, WBC and platelets, opsonize these cells for phagocytosis SLE is a complex disorder of multifactorial origin
resulting from genetic, immunologic and environmental factors that act in concert to cause activation of helper T-Cells and B-Cells and result in the production of several species of pathologic autoantibodies.
Mechanism of Tissue Injury
Kidney:
Lupus nephritis Joints:
Synovitis, arthritis etc CNS:
Due to acute vasculitis Heart:
Pericarditis, non-bacterial verrucous endocarditis Lungs, Spleen, etc.
Splenomegaly, pleuritis
Morphology
Variable presentation according to organ
involved Unpredictable presentation and course of the
disease Chronic discoid lupus erythematosus Subacute cutaneous lupus erythematosus
Clinical Features
Chronic systemic inflammatory disease that
principally affects joints Non-suppurative proliferative and
inflammatory synovitis Often progress to ankylosis
Genetic susceptibility Arthritogenic antigen Autoimmunity
Anti IgG antibody (Fc portion)
Rheumatoid Arthritis
Chronic disease, characterized by:
Keratoconjunctivitis sicca (Dry Eyes) Xerostomia (Dry mouth)
Immunlogically mediated destruction of the lacrimal and salivary glands May be associated with other autoimmune
disorders SLE, RA, polymyositis, scelroderma, vasculitis,
thyroiditis, MCTD, etc.
Sjögren Syndrome
Chronic disease characterized by:
Chronic inflammation as a result of autoimmunity Widespread damage to small blood vessels Progressive interstitial and perivascular fibrosis
CREST syndrome Calcinosis Raynaud’s disease Esophageal dysmotility Sclerodactyly Telangiectasia
Systemic sclerosis (Scleroderma)
Clinical features, mixture of
SLE Systemic sclerosis Polymyositis
Serologically characterized by: Autoantibodies to ribonucleotide particle
containing U1 ribonucleoprotein.
Mixed Connective Tissue Diseases