The murine lymphocyte receptor for IgE. I. Isolation and characterization of the murine B cell Fc epsilon receptor and comparison with Fc epsilon receptors from rat and human.

The Fc receptor for IgE (Fc epsilon R) on murine B lymphocytes was studied by using BALB/c mice infected 12 to 18 days previously with Nippostrongylus brasiliensis. B cells were enriched in the Sephadex G-10-passed lymphocytes by treating with anti-Thy-1.2 and complement (C). After stripping any cytophilic Ig with low pH, the B cells were 125I surface labeled; subsequently the membranes were solubilized with nonionic detergent, and putative Fc epsilon R components were allowed to bind to IgE-coated adsorbents. Bound radiolabel was eluted with low pH, and when examined by SDS-PAGE, was found to consist primarily of a relatively broad band centered at 49,000 m.w. (49K). Fluid-phase IgE could prevent the binding of the 49K component to the IgE solid-phase adsorbents. Rebinding studies further indicated that the 49K component exhibited a specificity for IgE, thus confirming that the 49K component was the murine B lymphocyte Fc receptor for IgE (Fc epsilon R). Some rebinding to rabbit IgG was observed, and by using 2.4G2, the monoclonal anti-Fc gamma 2b receptor (Fc gamma 2bR) antibody to isolate the IgG2b receptor, a clear distinction between the FC gamma 2bR and the 49K IgE receptor was demonstrated by SDS-PAGE analysis. Rabbit IgG was thus found to interact with both the 49K Fc epsilon R and the 59K FC gamma 2bR. The murine B lymphocyte Fc epsilon R was compared with the human B cell Fc epsilon R from the RPMI 8866 cell line and with the high affinity Fc epsilon R on rat basophilic leukemia cells by one- and two-dimensional gel analyses. The lymphocyte Fc epsilon R from mouse and human was found to be quite similar with respect to m.w. (45 to 50K) and isoelectric point (pI 4.5 to 5.0), whereas the basophil Fc epsilon R differed in both aspects.