Modulation of Fc receptors on human peripheral blood lymphocytes by antisera against beta 2 microglobulin, Ia or immunoglobulin.

The association between Fc receptors and other surface molecules was examined by EA-rosette (EAR) inhibition experiments. Twenty to 30% EAR were detected in suspensions of peripheral blood lymphocytes from normal individuals. Anti-β microglobulin (βMi) sera fully suppressed EAR whereas anti-Ig, anti-Ia sera and heat aggregated IgG inhibited only 50–60% EAR. Thus almost half of the detected EAR were apparently not surface Ig positive B cells. Rabbit and monkey anti-βMi sera suppressed EAR effectively whereas rat and chicken antisera, despite strong βMi binding capacity, inhibited EAR poorly. The latter result was ascribed on the basis of immunofluorescent analysis to inadequate capping of βMi. Incubation of PBL with whole antisera suppressed EAR to a similar degree at either 0° or 37°, whereas F(ab′) fragments were inhibitory only at 37°. Taken together the results suggest that Fc receptors can be inhibited by antibodies with specificity against any cell surface antigen. The blocking mechanism may be due to steric hindrance by the Fc part of antibody molecules and/or F(ab′) fragment mediated co-capping.