Receptors for IgG and complement in human spleen lymphoid cells. Preferential binding of particulate immune complexes through complement receptors.

Human lymphoid spleen cells attached to Petri dishes by poly-L-lysine bind 51Cr-labeled erythrocytes coated with IgG antibodies or complement but not uncoated erythrocytes or those coated with IgM antibodies. The number of erythrocytes bound through complement receptors is several times larger than that bound through IgG receptors. Increasing up to five times the number of IgG molecules on the red blood cells only leads to a slight increase of binding. However, the addition of complement to the IgG-coated erthrocytes increases 10 times the binding to spleen cells, even in the presence of an excess of normal IgG. These results can be explained by postulating that there is a larger number (or greater affinity) of spleen cell receptors for complement than that of spleen cell receptors for IgG.