General Pathology-2 Slides PDF

Dr. Mohammed Abdellah General Pathology-2 sinaiuniversity. net • DISORDERS OF IMMUNE REACTION (2) By the end of lecture you should be able to understand: . -DISORDERS OF IMMUNE REACTION. TYPE II HYPERSENSITIVITY (Cytotoxic Hypersensitivity):. Mechanism: The antigen is a component of a cell mem...

Dr. Mohammed Abdellah General Pathology-2 sinaiuniversity. net • DISORDERS OF IMMUNE REACTION (2) By the end of lecture you should be able to understand: . -DISORDERS OF IMMUNE REACTION. TYPE II HYPERSENSITIVITY (Cytotoxic Hypersensitivity):. Mechanism: The antigen is a component of a cell membrane. The antibodies are of the IgG and IgM classes. The reaction requires complement activation. The target cells undergo lysis. Examples: Incompatible blood transfusion. Rh incompatibility (erythroblastosis foetalis). Some types of rejection of transplanted organs. Autoimmune hemolytic anaemias. TYPE III HYPERSENSITIVITY (Immune Complex Reaction): Mechanism: The antibodies (IgG and IgM) combine with the antigen producing immune complex. The immune complexes are trapped within the vascular basement membranes. Complement activation leads to lysis and destruction of the basement membrane. Examples: -Acute proliferative post-streptococcal glomerulonephritis. -Arthus reaction: Repeated subcutaneous injection of antigens(e.g. insulin) producing local vasculitis, necrosis and oedema. Serum sickness: - The antigen is serum- injected for the first time in large amounts. - Part of the antigen will, still be present by the time the antibodies are formed (about 10 days after injection of the antigen). - Immune complexes are formed producing systemic manifestations including: Urticaria, fever, joint pains, generalized lymph node enlargement and glomerulonephritis. Some autoimmune diseases as SLE. TYPE IV HYPERSENSITIVITY (Delayed Hypersensitivity) Mechanism: The antigen is a part of a microorganism: bacteria as tuberculosis ,virus , fungus or parasite The antigen stimulates T lymphocytes Sensitized T lymphocytes lymphokines of several types, of which some cell mediated immunity (e.g. by attracting macrophages & inhibiting their migration from the area) & other lymphokines cause necrosis. TYPE IV HYPERSENSITIVITY (Delayed Hypersensitivity) Examples: Caseous necrosis in tuberculosis and tuberculin skin test. Cell-mediated graft rejection. Contact dermatitis. Some autoimmune diseases. Allergic contact dermatitis Autoimmunity -Loss of tolerance , where some of the normal tissue components are considered antigenic (autoantigens) autoantibodies tissue destruction & development of disease. Immunodeficency -Deficient response (immunodeficiency) involving B or T lymphocytes, macrophages , complement. -Congenital: as: X-linked agammaglobulinemia of Bruton, congenital thymic hypoplasia (DiGeorge syndrome), isolated IgA deficiency . -Acquired: AIDS, drug-induced immunodeficiency (e.g. immuran) & diabetes mellitus. II)AUTOIMMUNE DISEASES DEFINITION: These are hypersensitivity diseases resulting from destruction of one or more of the body tissues or organs by autoantibodies. due to a defect in the immune mechanism of self recognition; thus one of the body proteins is erroneously considered as "non-self" . MECHANISM: Altered tissue antigenicity may be drug-induced, or produced by actions of microorganisms. Cross reactions: This may occur between some human structures and certain microbes Mutations of immunocompetent cells. Release of isolated proteins e.g. thyroglobulin. Imbalance of suppressor-helper T cell function. Genetic factors play a role in some autoimmune diseases. Autoimmunity EXAMPLES : -Endocrine Diseases as Hashimoto's thyroiditis, 1ry myxoedema & 1ry Addison’s disease. -Some types of male infertility. -Autoimmune hemolytic anemia. -Gastrointestinal diseases as ulcerative colitis & Crohn’s disease. -Liver diseases as autoimmune hepatitis, 1ry biliary cirrhosis & primary sclerosing cholangitis. COLLAGEN DISEASES (Connective Tissue Diseases) Definition: A group of autoimmune diseases characterized by injury of collagen within & around vessels. Pathology: The fragmented collagen fibers resemble a mass of fibrin= fibrinoid necrosis or fibrinoid degeneration, accompanied by inflammation associated with increase of mucopolysaccharides within ground substance. Finally Fibrosis =the hallmark of disease state. COLLAGEN DISEASES (Connective Tissue Diseases) Collagen diseases include: -Rheumatic fever . -Rheumatoid arthritis. -Polyarteritis nodosa. -Systemic lupus erythematosus (SLE). -Scleroderma: characterized by systemic fibrosis affecting skin, GIT, lung, myocardium & kidneys. -Dermatomyositis: characterized by systemic muscle weakness (proximal > distal), eventually progressing to motor disability. In 50% of cases the disease is associated with skin rash . Thanks