Immune System Disorders What is an allergy anyway?

Response to antigens (allergens) leading to damage Response to antigens (allergens) leading to damage Require sensitizing dose(s) Require sensitizing dose(s) Hypersensitivity Reactions

Involve IgE antibodies Involve IgE antibodies Localized: Hives or asthma from contact or inhaled antigens Localized: Hives or asthma from contact or inhaled antigens Systemic: Shock from ingested or injected antigens Systemic: Shock from ingested or injected antigens Type I (Anaphylactic) Reactions Figure 19.1a

Skin testing Skin testing Desensitizati on Desensitizati on Type I (Anaphylactic) Reactions Figure 19.3

Involve IgG or IgM antibodies and complement Involve IgG or IgM antibodies and complement Complement activation causes cell lysis or damage by macrophages Complement activation causes cell lysis or damage by macrophages Type II (Cytotoxic) Reactions

Hemolytic Disease of the Newborn Figure 19.4

Drug-induced Thrombocytopenic Purpura Figure 19.5

IgG antibodies and antigens form complexes that lodge in basement membranes. IgG antibodies and antigens form complexes that lodge in basement membranes. Type III (Immune Complex) Reactions Figure 19.6

Delayed-type hypersensitivitie s due to T D cells Delayed-type hypersensitivitie s due to T D cells Cytokines attract macrophages and initiate tissue damage Cytokines attract macrophages and initiate tissue damage Type IV (Cell-Mediated) Reactions Figure 19.8

Clonal deletion during fetal development ensures self-tolerance Clonal deletion during fetal development ensures self-tolerance Autoimmunity is loss of self-tolerance Autoimmunity is loss of self-tolerance Autoimmune 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 Diseases

Histocompatibility antigens: Self antigens on cell surfaces Histocompatibility antigens: Self antigens on cell surfaces Major histocompatibility complex (MHC): Genes encoding histocompatibility antigens Major histocompatibility complex (MHC): Genes encoding histocompatibility antigens Human leukocyte antigen (HLA) complex: MHC genes in humans Human leukocyte antigen (HLA) complex: MHC genes in humans Reactions Related to the Human Leukocyte Antigen (HLA) Complex

Diseases Related to Specific HLAs Table 19.3

HLA Typing Figure 19.1

Transplants may be attacked by T cells, macrophages, and complement-fixing antibodies. Transplants may be attacked by T cells, macrophages, and complement-fixing antibodies. Transplants to privileged sites do not cause an immune response. Transplants to privileged sites do not cause an immune response. Stem cells may allow therapeutic cloning to avoid rejection. Stem cells may allow therapeutic cloning to avoid rejection. Reactions to Transplantation

Autograft: Use of one's own tissue Autograft: Use of one's own tissue Isograft: Use of identical twin's tissue Isograft: Use of identical twin's tissue Allograft: Use of tissue from another person Allograft: Use of tissue from another person Xenotransplantation product: Use of non- human tissue Xenotransplantation product: Use of non- human tissue Graft-versus-host disease can result from transplanted bone marrow that contains immunocompetent cells Graft-versus-host disease can result from transplanted bone marrow that contains immunocompetent cells Grafts

Cyclosporine suppresses IL-2 Cyclosporine suppresses IL-2 Mycophenolate mofetil inhibits T cell and B cell reproduction Mycophenolate mofetil inhibits T cell and B cell reproduction Sirolimus blocks IL-2 Sirolimus blocks IL-2 Immunosuppression prevents an immune response to transplanted tissues

Congenital: Due to defective or missing genes Congenital: Due to defective or missing genes Selective IgA immunodeficiency Selective IgA immunodeficiency Severe combined immunodeficiency Severe combined immunodeficiency Acquired: Develop during an individual's life, due to drugs, cancers, infections Acquired: Develop during an individual's life, due to drugs, cancers, infections Artificial: Immunosuppression drugs Natural: HIV infections Immune Deficiencies

Cancer cells possess tumor-specific antigens Cancer cells possess tumor-specific antigens T C cells recognize and lyse cancer cells T C cells recognize and lyse cancer cells Cancer cells may lack tumor antigens or kill T C cells Cancer cells may lack tumor antigens or kill T C cells The Immune System and Cancer Figure 19.11

Treatment of cancer using immunologic methods Treatment of cancer using immunologic methods Tumor necrosis factor, IL-2, and interferons may kill cancer cells Tumor necrosis factor, IL-2, and interferons may kill cancer cells Immunotoxins link poisons with an monoclonal antibody directed at a tumor antigen Immunotoxins link poisons with an monoclonal antibody directed at a tumor antigen Vaccines contain tumor-specific antigens Vaccines contain tumor-specific antigens Immunotherapy