Fig. 1.

Differential BCR-induced Ca²⁺ responses and its modulation by CD40 co-stimulation in Bal-17 and WEHI-231 cells. B cells were pretreated with 5 µg/ml of α-IgM (Aa, Ba) or α-IgM+CD40L (0.5 µg/ml) (Ab, Bb) for 0.5, 2, 4, 8, 24, and 48 hr. After harvesting the cells, the pre-treatment agents were removed, and α-IgM (5 µg/ml)-triggered [Ca²⁺]_i increases were measured in 1.5 mM [Ca²⁺]_o containing normal Tyrode solution. Representative [Ca²⁺]_i traces obtained from each B cell type are drawn, and the duration of α-IgM pre-stimulation (0, 2, 8, and 24 hr) are indicated inside the figure. (Ac, Bc) Δ[Ca²⁺]_i values (difference between the resting and peak [Ca²⁺]_i levels) were calculated and normalized against Δ[Ca²⁺]_i values of un-stimulated control cells. Changes in Δ[Ca²⁺]_i values are plotted against the duration of pre-stimulation. All experiments were repeated at least three times, and the detailed values are described in the text. ^*p<0.05.