Persistent reduction in anti-A Ab levels in the sera of mice that received A-BSA/anti-BSA Abs and CsA. Balb/c mice received an intraperitoneal injection of A-BSA (100 μg/mouse). After 6 hours, rabbit anti-BSA Abs were injected into the mice. Furthermore, the mice received daily injection of CsA at dose of 10 mg/kg/day. Untreated mice and mice that received injections of either A-BSA or CsA alone were used as controls. At 14 days after injection of A-BSA/anti-BSA Ab, the mice were intraperitoneally immunized with 5 × 10⁸ A-RBCs. (A) The levels of anti-A IgM in the sera of these mice were determined by ELISA assay before and after treatment (0, 1, 14, and 22 days after A-BSA/anti-BSA Ab injection). Average values (± SEM) for the individual groups are shown. The number of animals in each group was as follows: untreated control, n = 6; mice receiving CsA alone, n = 5; mice that received 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. *P < .05. (B) Anti-A Ab-producing cells in the Spl of each mouse were detected by the ELISPOT assay (22 days after the A-BSA/anti-BSA Ab injection).