Proliferation rates of the stimulated wild-type and Sap-deficient B cells. □ and ▪ columns represent the wild-type and Sap-deficient B cells, respectively. Cells were cultured for 3 days or 6 days. Average values (cpm) of incorporated [³H]-thymidine, ± standard deviations, are shown. A similar pattern was observed in 3 other independent experiments.