IL-4 enhances CLL cell activation in response to BCR crosslinking. (A-B) Responsiveness of CLL samples to BCR crosslinking is correlated with pCD79 protein levels. CLL samples were stimulated with anti-IgM antibody (αIg; 10 μg/mL) for 0 and 5 minutes. The correlation of pSYK (A) and pERK (B) to CD79b protein expression is analyzed. (C-D) IL-4 enhances pSYK and pERK in CLL samples stimulated by BCR crosslinking. U-CLL samples (C) and M-CLL samples (D) were cocultured in the presence (IL-4) or absence (MED) of IL-4 (25 ng/mL) for 48 hours. Viable CLL cells were stimulated with anti-IgM antibody (αIg; 10 μg/mL) for 0, 5, and 15 minutes. Phosphorylation of SYK and ERK was examined by immunoblot. Membranes were stripped and reprobed with SYK- and ERK-specific antibodies as loading controls. (E) IL-4 breaks down CLL cell anergy. Anergic CLL samples were cocultured in the presence (IL-4) or absence (MED) of IL-4 (25 ng/mL) for 48 hours. Viable CLL cells were stimulated with anti-IgM antibody (αIg; 10 μg/mL) for 0, 5, and 15 minutes. Phosphorylation of SYK and ERK was examined by immunoblot. Membranes were stripped and reprobed with SYK- and ERK-specific antibodies as loading controls. Left panels in (C-E) show 1 representative experiment; right panels represent the summarized results. Lines represent mean ± SEM of 6 samples. *P < .05; **P < .01.