Sometimes the immune response is overreactive against foreign antigen Or reacts against it's own tissue.
Hypersensitivity reaction can be classified according to the source of antigen Or basic Immunologic mechanisms causing the injury. Four type of hypersensitivity reactions -
Type 1: lgE- Mediated Reaction
Type 2: Cytotoxic
Type 3: Immune - Complex
Type 4: Delayed hypersensitivity
Type 1: lge mediated reaction:- Anaphylactic reaction are type 1 reaction that occur only in susceptible people who are highly sensitized to specific allergens. IgE antibodies, produced in response to the allergen, have a characteristics property of attaching to mast cell and basophils.
Type 2: Cytotoxic and Cytolytic reaction:- are type 2 hypersensitivity reaction involving the direct binding of IgG or IgM antibodies to an antigen on the cell surface. Antigen - antibody complexes activate the complement system, which mediates the reaction. Cellular tissue is destroyed in one of two ways (1) activation of the complement system resulting in cytolysis or (2) enchanced phagocytosis.
Type 3: Immune- Complex Reaction:- tissue damage in immune - complex reaction, which are type 3 reaction, occur secondary to antigen- antibody complexes. Soluble antigen combine with immunoglobulin of the IgG and IgM classes to from complexes that are too small to be effectively removed by the mononuclear Phagocyte system.
Type 4: Delayed hypersensitivity reaction:- A delayed hypersensitivity reaction- a type 4 reaction is also called a cell mediated immune response. Although cell- mediated response are usually protective mechanisms, tissue damage occur in delayed hypersensitivity reaction.
No comments:
Post a Comment