Differential expression of three CD45 alternative structures on murine T cells: exon 6-dependent epitope as a marker for functional heterogeneity of CD4 T cells.

We prepared a novel rat mAb specific for CD45 molecules bearing the epitope coded for by the alternative exon 6 of the murine CD45 gene (CD45RC). Together with available mAbs to alternative exon 4- and 5-dependent epltopes (CD45RA and CD45RB respectively), we found that the three alternative exons show differential expressions on murine lymphocytes. Flow cytometry analysis revealed that although B cells were homogeneously CD45RABC, the CD4 T cells clearly included two populations, CD45RABC and CD45RABC. The CD8 T cells were separated Into CD45RABC and CD45RABC populations. Such features of epitope expression on the cell surface correlate well with message levels of corresponding alternative exons. In the CD4 T cells, messages of alternative exons were associated with either one or two exon forms of the CD45 transcript. In CD8 T cells, there were transcripts with one, two, or three alternative exons. When stimulated by an Immobilized CD3 mAb, the CD45RCCD4 T cell subset preferentially secreted IL-2 and CD45RCCD4+ T cells produced IL-4. Upon stimulation with concanavalin A, CD45RCCD4 T cells converted to CD45RC cells, and the level of CD45RC expression on the CD45RCCD4 T cell subset was up-regulated. These changes were unidirectional and Irreversible. Therefore, differential expression of CD45RC probably delineates the functional heterogeneity of murine CD4 T cells that is associated with the stages of CD4 T cell maturation or activation. [ABSTRACT FROM PUBLISHER]