Figure 2.
Activation of B cells by surface immunoglobulin M (sIgM) cross-linking, but not by CD40 ligation, results in the induction of CD5 expression. B cells were cultured for 42 hr in the presence of DAP3 cells alone (a), in the presence of CD40 ligand (CD40L)–DAP3 transfectants (b), in the presence of goat anti-bovine IgM F(ab′)2 (25 µg/ml) (c), or in the presence of both goat anti-bovine IgM and CD40L–DAP3 cells (d), and then analysed by flow cytometry. Results are representative of four independent experiments performed on three separate animals. (e) Activation of B cells by sIgM cross-linking results in a higher level of CD5 mRNA expression compared to levels observed for B cells activated through CD40 or CD40 combined with sIgM cross-linking. B cells were cultured, for 12 or 24 hr, in the presence of CD40L–DAP3 transfectants, in the presence of goat anti-bovine IgM F(ab′)2 (10 µg/ml), or in the presence of both goat anti-bovine IgM and CD40L–DAP3 cells, and analysed for CD5 mRNA expression by using the RNase protection assay. This experiment is representative of results obtained from three separate ribonuclease protection assays (RPAs) and one reverse transcription–polymerase chain reaction (RT–PCR) experiment.