Hypersensitivity reactions
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The Correct Answer is BHYPERSENSITIVITY
| Hypersensitivity Type | AB | Complement | effector cells | Examples |
| Type I (immediate) | IgE | No | Basophil, mast cell | Anaphylaxis, hay fever, insect venom sensitivity, asthma |
| Type II (cytotoxic) | IgG, IgM | Yes | PMN K cell | Autoimmune hemolytic anemia. erythroblastosis fetalis, Goodpasture's syndrome |
| Type III (immune complex) | IgG. IgM | Yes | PMN , M | Serum sickness. SLE, R4, Glomeruloneplnritis, Arthritis |
| Type IV (delayed-cell mediated type ) | None | No | CTL TH1, M | Tuberculin test, poison ivy, contact dermatitis, transplant rejection. |
Type I (immediate): Anaphylactic & atopic, Ag cross-links IgE on presensitized mast cells & basophils, triggering release of Vasoactive amines. Reaction develops rapidly after Ag exposure due to performed Ab.
Type II (cytotoxic): IgM, IgG bind to Ag on enemy cell. leading to lysis by complement or phagocytosis.
Type III (immune complex)
Immune complex: Ag-Ab complexes activate complement. which attracts neutrophils. neutrophils release lysosomal enzymes .
Serum sickness:An Immune complex disease in which Abs to the foreign proteins are produced (5 days). Immune complexes form & are deposited in membranes, where they fix complement, more common than Arthus reaction.
Arthus Reaction: A local subacute Ab mediated hypersensitivity reaction. Intradermal injection of Ag induces antibodies, which form Ag-Ab complexes in the skin Charaeterized by edema, necrosis, & activation of complement.
Type IV (delayed, cell mediated type): Sensitized T lymphocytes encounter antigen & then release lymphokines lead to macrophage activation.
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