Induction of plasma cells by triggering via CD27 on B cells. (A) Highly purified peripheral blood B cells were cultured with 100 ng/mL IL-10 in the presence of mock transfectants (a), CD70 transfectants (b), or CD70 transfectants plus anti-CD70 MoAb 2 μg/mL (c) for 8 days, cytospun, and stained with May-Giemsa staining. The results are representative of 12 experiments using different donors. (B) Cultured B cells in the presence of 100 ng/mL IL-10 (○) or IL-10 + IL-2 50 U/mL (•) were stained with May-Giemsa staining and counted for plasma cells and B cells. Transfectants and apparent dead cells were eliminated from the cell count. Horizontal bars represent mean values. (C) Percentage of plasma cells cultured with indicated various concentrations of IL-10 in the presence of mock transfectants (○) or CD70 transfectants (•). Values are the mean ± SD of three experiments.