Mechanisms of red cell destruction mediated by non-complement binding IgG antibodies: the essential role in vivo of the Fc part of IgG.

F(ab')2G anti-D was prepared by limited digestion of IgG anti-D with pepsin. Conditions of digestion were chosen in order to obtain a nearly complete conversion of the anti-D antibody molecules as tested by immunochemical and serological techniques. The F(ab')2G anti-D was not capable of inducing adherence of rhesus D positive red cells to monocytes in vitro or of eliminating such cells in vivo in normal volunteers. These findings are compatible with a role of the Fc-receptor-mediated adherence to cells of the macrophage system in vivo in the destruction of erythrocytes by non-complement binding IgG antibodies.