Regulation of TOSO and apoptosis resistance. (A) TOSO mRNA expression after 24-hour incubation with B-cell receptor (BCR) stimulation, recombinant CD40L-expressing feeder cell lines, and combined BCR/CD40L stimulus; significant increase of TOSO by BCR stimulus (P = .013) and suppression by CD40L (P = .007). (B) Time-dependent course of TOSO expression at time points of 3, 24, 48, and 72 hours. (C) Percentage of apoptosis in CLL cells assessed by annexin V/7-AAD flow cytometry. Significantly decreased apoptosis rate by BCR stimulation (P = .003); CD40L nonsignificantly reduces apoptosis. Slightly elevated apoptosis in CD40L-treated CLL cells by addition of the FAS-agonistic antibody CH11. (D) TOSO protein expression after 72-hour incubation with B-cell receptor stimulus (BCR), recombinant CD40L-expressing feeder cell lines, and combined BCR/CD40L stimulus; increase of TOSO by BCR stimulus and suppression by CD40L. Densitometry quotient of TOSO/β-actin is indicated accordingly. Box plots in panels A and C show median, 1st and 3rd quartiles, and whiskers (error bars) defined by, at most, 1.5× IQR.