Characterization of the low-affinity receptor for IgE on murine B cells by using membrane impermeant cross-linking reagents.

The murine B lymphocyte receptor for the Fc portion of IgE (Fc epsilon R) was further characterized by using the membrane impermeable cross-linking reagents 3,3'-dithiobis-(sulfosuccinimidyl) proprionate (DTSSP) and bis-(sulfosuccinimidyl) suberate (BS3). IgE could be cross-linked to the Fc epsilon R on the intact cells with either reagent and, in addition, up to 10% of the B cell surface immunoglobulin (sIg; both IgM and IgD) was also found to cross-link to the IgE/Fc epsilon R complex. Analysis of isolated sIg/IgE/Fc epsilon R complexes indicated that about 60% of the Fc epsilon molecules were becoming cross-linked to sIg. Thus, the data suggest that on the intact murine B cell the Fc epsilon R is frequently in close association with sIg. The murine B cell Fc epsilon R was also examined for the presence of receptor-associated proteins that are buried in the membrane. Advantage was taken of the membrane-impermeant nature of DTSSP and BS3. IgE was cross-linked to the Fc epsilon R on intact cells by using the disulfide-cleavable DTSSP and following solubilization with nonionic detergent; BS3 was used to cross-link possible internal membrane components to the Fc epsilon R. In these experiments, the high-affinity Fc epsilon R on rat basophilic leukemia (RBL) cells could be cross-linked to a nonreducible high molecular weight complex of 100 kilodaltons. However, when intact murine B cells were treated with DTSSP, solubilized and treated with BS3 in the same manner as indicated above, no evidence was found for the presence of membrane-buried receptor-associated proteins with the B cell Fc epsilon R. 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.