The murine lymphocyte receptor for IgE. III. Use of chemical cross-linking reagents to further characterize the B lymphocyte Fc epsilon receptor.

Abstract

Cross-linking reagents were used to further characterize the murine B cell receptor for the Fc portion of IgE (Fc epsilon R) and compare this receptor to the well-characterized high-affinity Fc epsilon R on rat basophilic leukemia (RBL) cells. The disulfide cleavable and noncleavable reagents 3,3'-dithiobis(sulfosuccinimidyl) propionate (DTSSP) and bis(sulfosuccinimidyl) suberate (BS3) were used. With these reagents, efficient cross-linking of the alpha component of the high-affinity RBL Fc epsilon R to the membrane-buried beta and gamma components occurred only if the membrane was solubilized before the cross-linking reaction. In studies with purified murine B cells, IgE could be cross-linked to the Fc epsilon R on intact cells with either DTSSP or BS3. Under the same conditions, up to 10% of the B cell surface immunoglobulin (sIg) (both IgM and IgD) was also found to cross-link to a portion of the IgE/Fc epsilon R complex, suggesting that on the intact murine B cell the Fc epsilon R is frequently in close association with sIg. The B cell Fc epsilon R was also examined for the presence of receptor-associated proteins. Under conditions where the high-affinity RBL Fc epsilon R was substantially cross-linked to the alpha, beta, gamma complex, no evidence was seen for similar cross-linking of the B cell Fc epsilon R. Cross-linking experiments on affinity-purified Fc epsilon R preparations also gave no evidence for receptor-associated proteins with the B cell Fc epsilon R, although evidence for receptor-receptor association was seen. Thus, these data further support the concept that there may be little relationship between the high-affinity mast cell/basophil Fc epsilon R and the low-affinity lymphocyte Fc epsilon R.