All of the following are effector mechanisms of antibody-mediated disease EXCEPT:

Question

A. Opsonization and phagocytosis of cells
B. Fas-dependent apoptosis of cells
C. Complement- and Fc receptor-mediated inflammation and tissue injury
D. Antibody stimulation of cell surface receptors in the absence of the physiologic ligands
E. Fc?R crosslinking

Answer 1

ANS: B. Fas-dependent apoptosis is a regulatory mechanism in T cell-mediated responses and may be involved in T cell-mediated damage to other cells, but the Fas pathway is not stimulated by antibodies. Antibody-mediated (types I to III) hypersensitivity diseases involve four main effector mechanisms: (1) IgE coats mast cells and links the presence of allergens with mast cell activation and release of inflammatory mediators; (2) antibody-mediated opsonization of cells and activation of complement promotes phagocytosis of cells through phagocyte Fc or C3 receptors; (3) antibody binding to tissues can promote recruitment of leukocytes via binding to Fc receptors on leukocytes or by activation of complement with release of chemotactic byproducts; and (4) autoantibodies specific for cell surface receptors either stimulate receptor activity in the absence of the physiologic ligand or inhibit binding of physiologic ligands to their receptors.