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Disorders Associated with the
Immune System
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Immune disorder
Autoimmune Hypersensitivity Immune Deficiencies
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Disorders Associated with the Immune System
• Infection and immunosuppression are failures of the immune system.
• Superantigens cause release of cytokines that cause adverse host responses.
• Allergies and transplant rejection are harmful immune reactions
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• Response to antigens (allergens) leading to damage
• Require sensitizing dose(s)
Hypersensitivity Reactions
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• Involve IgE antibodies
• Localized: Hives or asthma from contact or inhaled antigens
• Systemic: Shock from ingested or injected antigens
Type I (Anaphylactic) Reactions
Figure 19.1a
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• Skin testing• Desensitization
Type I (Anaphylactic) Reactions
Figure 19.3
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• Involve IgG or IgM antibodies and complement
• Complement activation causes cell lysis or damage by macrophages
Type II (Cytotoxic) Reactions
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ABO Blood Group System
Table 19.2
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Hemolytic Disease of the Newborn
Figure 19.4
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Drug-induced Thrombocytopenic Purpura
Figure 19.5
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• IgG antibodies and antigens form complexes that lodge in basement membranes.
Type III (Immune Complex) Reactions
Figure 19.6
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• Delayed-type hypersensitivities due to TD cells
• Cytokines attract macrophages and initiate tissue damage
Type IV (Cell-Mediated) Reactions
Figure 19.8
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Comparison of Different Types of hypersensitivity
characteristics type-I (anaphylactic)
type-II (cytotoxic)
type-III(immune complex)
type-IV(delayed type)
antibody IgE IgG, IgM IgG, IgM None
antigen exogenous cell surface soluble tissues & organs
response time 15-30 minutes minutes-hours 3-8 hours 48-72 hours
appearance weal & flare lysis and necrosis
erythema and edema, necrosis
erythema and induration
histology basophils and eosinophil
antibody and complement
complement and neutrophils
monocytes and lymphocytes
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histology basophils and eosinophil antibody and
complement
complement and neutrophils
monocytes and lymphocytes
transferred with antibody antibody antibody T-cells
examplesallergic
asthma, hay fever
Erythroblastosis fetalis, Goodpasture's nephritis
SLE, farmer's lung disease
tuberculin test, poison ivy, granuloma
Comparison of Different Types of hypersensitivity
characteristics type-I (anaphylactic)
type-II (cytotoxic)
type-III(immune complex)
type-IV(delayed type)
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• Molecular Mimicry: Due to antibodies against pathogen’s epitope that is identical to a self antigen e.g Streptococcus gp A and rheumatic fever.
• Modification of cell-surface antigens : eg. Thermbocytopenia (low level of platelets) and anemia (low level of RBC) due to sulfa drugs.
• Availability of normally sequestered self-Ag: The emberyonic Ags are not recognized as self present in very low concn. to induce autoimmune dis. Some cases as in thyroid and testes
Hypothesis of Autoimmune Diseases
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• Clonal deletion during fetal development ensures self-tolerance
• Autoimmunity is loss of self-tolerance
Autoimmune Diseases
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• 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
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• Histocompatibility antigens: Self antigens on cell surfaces
• Major histocompatibility complex (MHC): Genes encoding histocompatibility antigens
• Human leukocyte antigen (HLA) complex: MHC genes in humans
Reactions Related to the Human Leukocyte Antigen
(HLA) Complex
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Diseases Related to Specific HLAs
Table 19.3
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HLA Typing
Figure 19.1
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Spectrum of autoimmune diseases, target organs and diagnostic tests
Disease Organ Antibody to Diagnostic Test
Hashimoto's thyroiditis
Thyroid Thyroglobulin, thyroid peroxidase (microsomal)
RIA, Passive, CF, hemagglutination
Primary Myxedema
Thyroid Cytoplasmic TSH receptor
Immunofluorescence (IF)
Graves' disease Thyroid Bioassay, Competition for TSH receptor
Pernicious anemia Red cells Intrinsic factor (IF), Gastric parietal cell
B-12 binding to IF immunofluorescence
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Addison's disease Adrenal Adrenal cells Immunofluorescence
Premature onset menopause
Ovary Steroid producing cells
Immunofluorescence
Male infertility Sperm Spermatozoa Agglutination, Immunofluorescence
Insulin dependent juvenile diabetes
Pancreas Pancreatic islet beta cells
Disease Organ Antibody to Diagnostic Test
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Insulin resistant diabetic
Systemic Insulin receptor Competition for receptor
Myasthenia graves
Muscle Muscle, acetyl choline receptor
Immunofluorescence, competition for receptor
Rheumatoid
arthritisSkin, kidney,
joints etcIgG IgG-latex
agglutination
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Rheumatoid arthritis
Skin, kidney, joints etc
IgG IgG-latex agglutination
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• 1ry =Congenital: Due to defective or missing genes– Selective IgA immunodeficiency– Severe combined immunodeficiency
• 2ry= Acquired: Develop during an individual's life, due to drugs, cancers, infections– Artificial: Immunosuppression drugs– Natural: HIV infections
Immune Deficiencies
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Treatment
• Anti-inflammatory (corticosteroid) and immunosuppressive (cyclosporin) drug therapy is the present method of treating autoimmune diseases.
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PRIMARY IMMUNODEFICIENCIES
Primary immunodeficiencies are inherited defects of the immune system. These defects may be in the specific or nonspecific immune mechanisms. They are classified on the basis of the site of lesion in the developmental or differentiation pathway of the immune system.
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Disorders of lymphoid stem cells
Severe combined Immunodeficiency: (SCID).
Patients with SCID are susceptible to a variety of bacterial, viral, mycotic and protozoan + TB infections.
Diagnosis is based on enumeration of T and B cells and immunoglobulin measurement
Severe combined immunodeficiency can be treated with bone marrow transplant
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I. Disorders of T cells
• A) DiGeorge's syndrome: This the most clearly defined T-cell immunodeficiency
• Recurrent intercellular bacterial (eg. TB) and fungal infection infections
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• B) Wiskott-Aldrich syndrome • This syndrome is associated with
normal T cell numbers with reduced functions
• Boys with this syndrome develop severe eczema, petechia (Fungal Infection)
I. Disorders of T cells
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• C) Bare leukocyte syndrome • MHC deficiency• these patients have fewer CD4 cells
and are infection prone
I. Disorders of T cells
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II. Disorders of B lymphocytes
• x-linked infantile hypogammaglobulinemia • Transient hypogammaglobulinemia • IgA deficiency • Selective IgG deficiency • These patients are susceptible to pyogenic
infections.
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III. Defects of the phagocytic system
• A) Chronic granulomatous disease (CGD)
• Leukocytes have poor intracellular killing and low respiratory burst.
• B) Chediak-Higashi syndrome • inability of phagosome and lysosome
fusion and proteinase deficiency
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Acquired Immunodeficiency Syndrome (AIDS)
• 1981 In U.S., cluster of Pneumocystis and Kaposi's sarcoma in young homosexual men discovered. The men showed loss of immune function.
• 1983 Discovery of virus causing loss of immune function.
SCONDRY IMMUNODEFICIENCIES
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Acquired Immunodeficiency Syndrome (AIDS)
Figure 19.12a
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HIV Infection
Figure 19.12b