Novel roles for murine complement receptors type 1 and 2 II. Expression and function of CR1/2 on murine mesenteric lymph node T cells.

In mice CR1 and CR2 are encoded at a single locus and the two alternatively spliced RNA transcripts of the CD21 gene generate murine CR1 and CR2 (CR1/2). While the function of CD21 has been extensively studied on murine B lymphocytes, much less is known about its appearance and role on T cells. Earlier we had demonstrated the expression of CR1/2 on activated murine T cells by cytofluorymetry and immunoprecipitation and proposed its role in the enhancement of antigen presentation by B cells and macrophages bearing C3-fragments. In this study we analyze the expression-profile and further possible roles of CR1/2 on T lymphocytes. We describe a CR1/2 expressing CD4+ T cell subpopulation present in the mesenteric lymph nodes of mice. We show that these cells can be activated by the CD21-specific 7G6 single chain antibody, and demonstrate that activation via this complement receptor results in the translocation of NF-kappaB to the nucleus. Interestingly we found a substantial elevation of CD21+ T cells during both spontaneous and ceramide-induced apoptosis.