Binding of circulating immune complexes to human peripheral blood lymphocytes: Effect of complement

Abstract

The mode of binding of immune complexes, with and without bound complement components, to normal human peripheral blood lymphocytes was examined. Heat-aggregated human IgG (agg IgG) was employed as an in vitro model of immune complexes. Immune complexes without bound complement or with bound C1, C4, or C2 inhibited antibody-dependent cellular cytotoxicity (ADCC) and EA rosette formation but not rosette formation with EAC. In contrast, immune complexes with bound C3b blocked EAC rosette formation but inhibited ADCC and EA rosette formation little if at all. These findings demonstrate that agg IgG, and thus immune complexes, without fixed complement or those with bound C1, C4, or C2, preferentially interact with the lymphocyte Fc receptor and that C3b-bound immune complexes bind to the lymphocyte surface C3b receptor.