The effects of IL-10 on proliferation and differentiation of B-CLL cells. (A) ³H-thymidine incorporation measured in 4 × 10⁵ MNCs following culture for 7 days with either medium alone, 5 to 100 ng/mL of IL-10, 100 ng/mL TPA, or TPA plus 5 to 100 ng/mL of IL-10. Experiments were performed in triplicate and represent the mean ± SEM for five B-CLL patients. (B) IgM concentration in supernatants from 4 × 10⁶ MNCs cultured under the same culture conditions as (A), but with 25 ng/mL of IL-10. Experiments in (B) were performed in triplicate and represent the mean ± SEM for 10 B-CLL patients. The MNCs studied for proliferation and differentiation contained a median of 96.5% CD19/CD5 positive B-CLL cells.