IMMUNOLOGY

Detailed explanation-1: -Type II hypersensitivity reaction refers to an antibody-mediated immune reaction in which antibodies (IgG or IgM) are directed against cellular or extracellular matrix antigens, resulting in cellular destruction, functional loss, or damage to tissues. Damage can occur through multiple mechanisms.

Detailed explanation-2: -Type I, II and III hypersensitivity reactions are known as immediate hypersensitivity reactions because they occur within 24 hours of exposure to the antigen or allergen. Immediate hypersensitivity reactions are predominantly mediated by IgE, IgM, and IgG antibodies.

Detailed explanation-3: -Similar to type 1, type 2 hypersensitivity reactions also involve antibodies. In fact, type 2 and type 3 hypersensitivity both result from the same class of antibody, called IgG. The difference between them lies in the form of antigens that generate a response. Additionally, type 2 can also involve IgM antibodies.

Detailed explanation-4: -Type II hypersensitivity reactions (Fig. 46-2) are caused by chemical modification of cell surface or matrix-associated antigens that generates “foreign” epitopes to which the immune system is not tolerant.