Immunoglobulin bound on the surface of bacteria mediates phagocytosis by:

Ans. (a) 3b and Fc Cells coated by antibodies are cleared through phagocytosis. These bacterial cells are recognized by phagocytic Fc receptors. In addition when IgM on IgG antibodies are deposited on the surfaces of cells they may activate the complement system by the classical pathway and generates C3b and C4b. C3b and C4b gets deposited over the surface of bacterial cell and are recognized by the phagocytes. The net result is phagocytosis. Remember: Antibody mediated destruction of cells may occur by antibody dependent cellular cytotoxicity (ADCC) also, where cells are lysed with out phagocytosis. ADCC is mediated by monocytes, neutrophills, eosinophils and NK cells.