FOXP1 is dependent upon CD40 stimulation for promotion of human B-cell expansion but not for repression of proapoptotic genes. Memory B cells were sorted from human peripheral blood and transduced with either FOXP1-IRES-YFP or control-IRES-YFP and cultured without CD40L-L cells as of day 3 after transduction. (A) The percentage of transduced cells in each culture was followed over time by FACS analysis and normalized to the percentage of transduced cells at day 3 after transduction. Mean ± SD of 3 independent experiments are shown. (B) Six days after transduction, YFP-positive cells were sorted. Gene expression levels of the proapoptotic genes were analyzed by qRT-PCR. Expression levels were normalized to expression levels in control-transduced cells. Mean ± SEM of six independent experiments are shown. (1-sample t test, **P < .01, ***P < .001).