Cdc42 is required to initiate the plasma cell differentiation program. (A) Splenic WT and Cdc42 KO B cells were stimulated with CD40L for 30 min. Western blot analysis shows phosphorylation of Akt, FoxO1, Erk, STAT3, and PAK1. Quantifications shown in charts under blots indicate intensity of proteins relative to total Erk as determined by densitometry. (B and C) qRT-PCR for mRNA of indicated genes of WT or Cdc42 KO B cells stimulated for 0 –2 h (B) or for 4 d (C) with CD40L (B and C) or LPS (C) in the presence of IL-4 and IL-5. mRNA expression was normalized against the levels of carboxypeptidase H (CPH) and is presented as fold increase over the no stimulated condition (B) or cells treated with IL-4 and IL-5 only (C). Data are representative of 3 independent experiments.