CD38 requires Lyn, Fyn, Btk, PI3K, and Erk, but not PLC-γ2 to promote differentiation of T2 B lymphocytes. (A) T2 B cells from CD38^−/−, Lyn^−/−, Fyn^−/−, Btk-deficient (Xid), or wild-type mice were stimulated 48 hours as indicated. (B) T2 B cells from wild-type mice were preincubated 30 minutes with inhibitory drugs and then stimulated as indicated, harvested at 48 hours, and restained with anti-B220, anti-CD21, and anti-CD24. The numbers show the percentage in each region and are representative from 3 independent experiments with similar results.