Developmental regulation of Fc epsilon RII/CD23 expression in B-lineage cells: evidence for transcriptional and post-transcriptional levels of control.

The present studies show that the expression of cell surface Fc epsilon RII/CD23, detected with the monoclonal anti-Fc epsilon RII/CD23 antibody B3B4 or by the binding of IgE, is not restricted to the stage of resting mature virgin B lymphocytes. Murine CD23 was detected as a cell surface protein on two sIgG+ B-cell lines. Moreover, we detected full-length transcripts for Fc epsilon RII/CD23 in several members of a panel murine B lymphoid lineage cell lines representative of all stages of murine B lymphocyte development. Our findings suggest that regulation of CD23 translation may differ between B-cell lines at various stages of differentiation. The detection of mRNA transcripts for Fc epsilon RII/CD23 was not restricted to transformed cell lines. Fc epsilon RII/CD23 transcripts were amplified by RT-PCR from peritoneal and splenic B lymphocyte subpopulations that were sorted by flow cytometry into populations that did not express surface Fc epsilon RII/CD23. Our findings suggest that Fc epsilon RII/CD23 transcription and translation are not necessarily restricted to the narrow developmental window of murine B lymphocyte differentiation as previously thought. Our findings imply that Fc epsilon RII/CD23 may be expressed at the protein level at various stages of murine B lymphocyte differentiation. Investigations into the expression patterns and potential mechanisms of regulation of Fc epsilon RII/CD23 could provide insight into the basis for the wide range of immunological functions that have been proposed for Fc epsilon RII/CD23.