Immune SystemImmune System Disorders Disorders

What is an allergy anyway?What is an allergy anyway?

Response to antigens (allergens) Response to antigens (allergens) leading to damageleading to damage

Require sensitizing dose(s)Require sensitizing dose(s)

Hypersensitivity Hypersensitivity ReactionsReactions

Involve IgE Involve IgE antibodiesantibodies

Localized: Localized: Hives or Hives or asthma from asthma from contact or contact or inhaled inhaled antigensantigens

Systemic: Systemic: Shock from Shock from ingested or ingested or injected injected antigensantigens

Type I (Anaphylactic) Type I (Anaphylactic) ReactionsReactions

Figure 19.1a

Skin testingSkin testing DesensitizatDesensitizat

ionion

Type I (Anaphylactic) Type I (Anaphylactic) ReactionsReactions

Figure 19.3

Involve IgG or IgM antibodies and Involve IgG or IgM antibodies and complementcomplement

Complement activation causes cell Complement activation causes cell lysis or damage by macrophageslysis or damage by macrophages

Type II (Cytotoxic) Type II (Cytotoxic) ReactionsReactions

Hemolytic Disease of Hemolytic Disease of the Newbornthe Newborn

Figure 19.4

Drug-induced Drug-induced Thrombocytopenic Thrombocytopenic

PurpuraPurpura

Figure 19.5

IgG antibodies and antigens form complexes IgG antibodies and antigens form complexes that lodge in basement membranesthat lodge in basement membranes..

Type III (Immune Complex) Type III (Immune Complex) ReactionsReactions

Figure 19.6

Delayed-type Delayed-type hypersensitivitihypersensitivities due to Tes due to TDD cellscells

Cytokines Cytokines attract attract macrophages macrophages and initiate and initiate tissue damagetissue damage

Type IV (Cell-Mediated) Type IV (Cell-Mediated) ReactionsReactions

Figure 19.8

Clonal deletion during fetal Clonal deletion during fetal development ensures self-tolerancedevelopment ensures self-tolerance

Autoimmunity is loss of self-Autoimmunity is loss of self-tolerancetolerance

Autoimmune DiseasesAutoimmune Diseases

Type I — Due to antibodies against pathogens

Type II — Antibodies react with cell-surface antigens

Type III (Immune Complex) — IgM, IgG, complement immune complexes deposit in tissues

Type IV — Mediated by T cells

Autoimmune DiseasesAutoimmune Diseases

Histocompatibility antigens: Self Histocompatibility antigens: Self antigens on cell surfacesantigens on cell surfaces

Major histocompatibility complex Major histocompatibility complex (MHC): Genes encoding (MHC): Genes encoding histocompatibility antigenshistocompatibility antigens

Human leukocyte antigen (HLA) Human leukocyte antigen (HLA) complex: MHC genes in humanscomplex: MHC genes in humans

Reactions Related to the Human Reactions Related to the Human Leukocyte Antigen (HLA) ComplexLeukocyte Antigen (HLA) Complex

Diseases Related to Diseases Related to Specific HLAsSpecific HLAs

Table 19.3

HLA TypingHLA Typing

Figure 19.1

Transplants may be attacked by T Transplants may be attacked by T cells, macrophages, and complement-cells, macrophages, and complement-fixing antibodies.fixing antibodies.

Transplants to privileged sites do not Transplants to privileged sites do not cause an immune response.cause an immune response.

Stem cells may allow therapeutic Stem cells may allow therapeutic cloning to avoid rejection.cloning to avoid rejection.

Reactions to Reactions to TransplantationTransplantation

Autograft: Use of one's own tissueAutograft: Use of one's own tissue Isograft: Use of identical twin's tissueIsograft: Use of identical twin's tissue Allograft: Use of tissue from another Allograft: Use of tissue from another

personperson Xenotransplantation product: Use of Xenotransplantation product: Use of

non-human tissuenon-human tissue Graft-versus-host disease can result Graft-versus-host disease can result

from transplanted bone marrow that from transplanted bone marrow that contains immunocompetent cellscontains immunocompetent cells

GraftsGrafts

Cyclosporine suppresses IL-2Cyclosporine suppresses IL-2 Mycophenolate mofetil inhibits T cell Mycophenolate mofetil inhibits T cell

and B cell reproductionand B cell reproduction Sirolimus blocks IL-2Sirolimus blocks IL-2

Immunosuppression Immunosuppression prevents an immune prevents an immune

response to transplanted response to transplanted tissuestissues

Congenital: Due to defective or missing Congenital: Due to defective or missing genesgenes Selective IgA immunodeficiencySelective IgA immunodeficiency Severe combined immunodeficiencySevere combined immunodeficiency

Acquired: Develop during an Acquired: Develop during an individual's life, due to drugs, cancers, individual's life, due to drugs, cancers, infectionsinfections Artificial: Immunosuppression drugs Natural: HIV infections

Immune DeficienciesImmune Deficiencies

Cancer cells possess tumor-specific antigensCancer cells possess tumor-specific antigens TTCC cells recognize and lyse cancer cells cells recognize and lyse cancer cells

Cancer cells may lack tumor antigens or kill TCancer cells may lack tumor antigens or kill TCC cells cells

The Immune System and The Immune System and CancerCancer

Figure 19.11

Treatment of cancer using Treatment of cancer using immunologic methodsimmunologic methods

Tumor necrosis factor, IL-2, and Tumor necrosis factor, IL-2, and interferons may kill cancer cellsinterferons may kill cancer cells

Immunotoxins link poisons with an Immunotoxins link poisons with an monoclonal antibody directed at a monoclonal antibody directed at a tumor antigentumor antigen

Vaccines contain tumor-specific Vaccines contain tumor-specific antigensantigens

ImmunotherapyImmunotherapy