Influence of CD20 on RTX inhibitory effect. (A) BCR was stimulated in RL cells pretreated during 16 hours with 10 μg/mL of entire RTX, F(ab′)2 RTX, Campath-H1, or nonrelevant human IgG. Results represent Syk activation (Y525) expressed in MFI and are the mean of 3 independent experiments ± SD. *P < .05; n.s indicates not significant. (B) Syk activation (Y525) was evaluated on CD20 high (clone 1G11) and CD20 low (clone 2B11) expressing cells preincubated with RTX (10 μg/mL, 16 hours) and stimulated with anti-IgM (10 μg/mL, 5 minutes). Nonstimulated and stimulated cells are represented by gray and black histograms, respectively. Histograms are representative of 3 independent experiments.