Absence of B cells with receptors for group A carbohydrates in mice that received A-BSA/anti-BSA Abs and CsA treatment. Mice that were either untreated or treated with CsA alone, a single injection of A-BSA/anti-BSA Abs, or A-BSA/anti-BSA Abs along with CsA were intraperitoneally immunized with a single injection (2 weeks after the injection of A-BSA/anti-BSA Abs) or 2 injections of 5 × 10⁸ A-RBCs (8 and 9 weeks after the injection of A-BSA/anti-BSA Abs). Spl and PerC cells were prepared from these mice 8 days after the last immunization (3 or 10 weeks after the injection of A-BSA/anti-BSA Abs). The cells were stained with FLUOS-conjugated A-BSA or control FLUOS-conjugated BSA along with biotinylated anti-mouse IgM mAb. The biotinylated mAb were visualized using allophycocyanin-streptavidin. Representative contour plots obtained by FCM analysis show an absence of A-BSA-binding B cells in the PerC (A,C) and Spl (B) of mice that received combined A-BSA/anti-BSA Abs and CsA treatment. To ensure statistical significance, data on 10⁵ PerC cells and 2 × 10⁵ Spl cells were collected for each sample. The frequency of A-BSA–binding B cells was calculated by subtracting the percentage of sIgM⁺ cells stained with control FLUOS-conjugated BSA from the percentage of sIgM⁺ cells stained with FLUOS-conjugated A-BSA. Percentages of total sIgM⁺ B cells are shown. Average values (± SEM) for the individual groups are shown (*P < .01 when compared with the data from the untreated control mice; #P < .01 when compared with the data from mice treated with CsA alone; and +P < .01 when compared with the data from mice treated with mice treated with A-BSA/anti-BSA Abs alone). (A,B) The number of animals in each group was as follows: untreated control, n = 6; mice that received CsA alone, n = 5; mice received only A-BSA/anti-BSA Abs alone, n = 5; and mice that received a single injection of A-BSA/anti-BSA Abs and daily administration of CsA, n = 5. (C) The number of animals in each group was as follows: untreated control, n = 5; mice receiving CsA alone, n = 4; and mice receiving a single injection of A-BSA/anti-BSA Abs and daily administration of CsA, n = 5.