CsA blocked CD5+ B-1 cell differentiation induced by cross-linking sIgM but not B-2 cell differentiation by CD40 ligation. The CFSE-labeled resting B cells from the untreated control mice were cultured in the presence of either soluble F(ab′)2 fragments of anti-IgM as an analog of TI-2 Ags or CD40L and IL-4 that provide thymus-dependent inductive signals for 3 days. CsA was added to the culture medium at various doses. The cultivated cells were stained with PE-conjugated CD19 or biotinylated CD5 mAb. The biotinylated mAb were visualized using allophycocyanin-streptavidin. (A) Representative contour plots obtained by FCM analysis are shown. The percentages of the total number of cultivated cells in each quadrant are shown. (B) The relationship between the concentration of CsA and its inhibitory effect on B-1a cell differentiation induced by anti-IgM F(ab′)2 fragments. The percentages of the total number of cultivated cells in each quadrant are shown.
