HYPERSENSITIVITY
CLASSICAL ALTERNATE AND LECTIN PATHWAYS
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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What is the mechanism of a type I hypersensitivity?
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Ag induces cross-linking of IgE bound to mast cells and basophils with release of vasoactive dilators
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Ab directed against cell surface antigens mediates cell destruction via complement activation or Ab-dependent cell-mediated cytotoxicity (ADCC). RBCs are common targets
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Ag-Ab complexes deposited in various tissues induce complement activation an dan ensuing inflammatory response mediated by massive infiltration of neutrophils
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sensitized T cells (TH1, TH2, and others) release cytokines that activate macrophages or TC cells, which mediate direct cellular damage
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Explanation:
Detailed explanation-1: -In general, a patient that presents with a type I hypersensitivity usually develops a reaction within one hour after exposure to an antigen. The signs and symptoms exhibited in this type of reaction involve vasoactive mediators that are released by IgE bound mast cells and basophils.
Detailed explanation-2: -In type I hypersensitivity, B cells are stimulated (by CD4+ Th2 cells) to produce IgE antibodies specific to an antigen. The difference between a normal infectious immune response and a type 1 hypersensitivity response is that in type 1 hypersensitivity, the antibody is IgE instead of IgA, IgG, or IgM.
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