Fig. 1.

RA inhibits BCR and CD38 ligation-induced B cell proliferation. Primary murine B cells were cultured in the presence and absence of a physiological concentration of RA (10 nM) and the stimuli indicated for 72 h. [³H]thymidine was added to the cells in the last 4 h of culture to label the proliferating cells, and [³H]thymidine incorporation was determined. (A) Proliferation of B cells stimulated with low doses of anti-μ.(B) Proliferation of B cells stimulated with anti-CD38. (C) Proliferation of B cells stimulated with anti-CD38 and anti-μ (each 1 μg/ml) in the presence and absence of RA. The data shown represent the mean ± SE for five independent experiments conducted in triplicate. *, P < 0.01.