Effects of a neutralizing antibody to human IL-10 on the proliferation of BCBL-1 and BC-1 cells. Cells (5 × 10³cells/microwell) from the BCBL-1 and BC-1 cell lines were cultured for 3 days with or without the addition of 25% autologous conditioned medium either alone or in the presence of a neutralizing MoAb (19F1; 5 μg/mL) to human IL-10 or an isotype-matched control MoAb (R35-95; 5 μg/mL). Sets of cultures were supplemented with recombinant human IL-10 (25 ng/mL). ³H thymidine was added during the final 20 hours of culture. The results represent the mean (±SD) radioactivity of triplicate cultures. Shown is a representative experiment of 4 performed.