Effects of FTY720 on serum antibody production. (A) SCID mice were adoptively transferred with 5 × 10⁶ normal PerC B cells and were treated with mock (•) or FTY720 (○) every 2 days. Two weeks after the transfer, serum was collected for the measurement of total immunoglobulin levels by ELISA. Horizontal bars represent the mean. (B) Mice pretreated with FTY720 and intraperitoneally immunized with heat-killed, pepsin-treated S pneumoniae strain R36A, received daily treatment with FTY720. After 5 days, serum anti-PC IgM was measured by ELISA. The error bars are ± SEM (n = 4) from 2 separate experiments.