Secreted IgM activates BCR signaling in TLR9-stimulated CLL. (A-B) Tyrosine-based activation of CD79A in DSP30-stimulated CLL cells cultured for the time as indicated. Comparison of ZAP-70–negative and ZAP-70–positive patient samples (encrypted and anonymized by V numbers) after 48 hours is depicted in panel B. (C) Concentrations of sIgM in CM derived from untreated (CM control) and DSP30-stimulated Zap-70–positive CLL cells before (CM DSP30) and after (CM DSP30-IgM) IgM depletion was performed. Data are presented in a bar diagram as the mean ± SEM of n = 4 patient samples. P values are indicated by asterisks: *P < .05. (D) Viability of DSP30-stimulated ZAP-70–negative B-CLL cells cultured in fresh media or in the respective CM derived from Zap-70–positive patient samples as shown in panel C. Data are presented as the mean ± SD of n = 3 patient samples in a bar diagram. P values are indicated by asterisks: **P < .01; *P < .05. (E) Activation of CD79A in DSP30-stimulated ZAP-70–negative B-CLL cells cultured in fresh media or in the respective CM derived from Zap-70–positive cells as shown in panel C. Data show western blot analysis of 1 representative patient sample out of n = 2 tested.