CD23 isoforms in murine T and B lymphocytes.

A major objective of the present studies was to seek biochemical evidence for the production of the low affinity IgE Fc receptor (CD23) by murine T cells. These studies have established that most of the murine T cell populations analyzed express CD23 mRNA. Some T cell populations contained a transcript whose nucleotide sequence was identical to that previously reported for the CD23 cDNA cloned from murine B cells. Some T and B cells contained CD23 transcripts lacking exon-3-encoded sequences. If translated, these transcripts would yield a CD23 polypeptide lacking the transmembrane segment and all but six amino acids of the intracytoplasmic tail. The truncated CD23 transcripts detected in T and B cells in these studies appear to be generated via alternative splicing. It is possible that these transcripts encode soluble, secretory forms of CD23, or that these transcripts have regulatory functions that influence CD23 gene expression. These investigations provide new information about the structure of murine lymphocyte CD23, they predict the occurrence of CD23 isoforms in the mouse, and they present direct evidence for the production of CD23 by murine T lymphocytes.