TNF-α secretion induced by hCD40-P227A versus WT hCD40. M12.hCD40WT (hCD40WT.1, hCD40WT.2) and M12.P227A (P227A.1, P227A.2) cells were stimulated for the indicated times and TNF-α ELISA was performed. Data are presented as means plus or minus SD of background-corrected TNF-α in replicate cultures from 3 separate experiments: (mean TNF-α induced by Hi5-hCD154) − (mean TNF-α induced by MDM2 control virus-infected Hi5). Asterisk denotes statistical difference (*P < .05) between hCD40WT and hCD40-P227A by 2-tailed Student t test.