sIgM and CD40 engagement favor survival of CLL B cells.
(A) Purified CLL cells were subjected to BCR engagement using goat anti-human IgM F(ab′)2 fragments over a range of doses. (B) Purification of CLL cells was confirmed by FACS for coexpression of CD5 and CD19. (C) The purified cells were cultured for 48 hours with media only, or stimulated by CD40 ligation (anti-CD40 mAb, murine IgGκ1, 2μg/mL), IgM engagement (goat anti-human IgM F(ab′)2, 10μg/mL), CD40 and IgM engagement, or dexamethasone (10−7 M). The percentage of apoptotic cells for each circumstance, measured by annexin V–FITC, is indicated. (D) Apoptosis was determined for cells of another case by the PI method after culture with media only, with anti-IgM F(ab′)2, or with a control polyspecific goat F(ab′)2. The percent of cells with subdiploid DNA (apoptotic percent) is indicated for each histogram. (E) Purified CLL cells were stimulated by CD40 and/or IgM engagement, dexamethasone, or exposed to control antibodies (anti-CD23, murine IgGκ1, 2 μg/mL; or polyspecific goat F(ab′)2, 10 μg/mL) and evaluated for apoptosis by the PI method. Error bars represent the SEM.
