Effects of FTY720 treatment on antibody production. At 14 days after immunization, bone marrow (BM), spleen, and serum samples from control (▪) or FTY720-treated (□) mice were collected. The number of splenic (A-B) or BM (C-D) NP-specific IgG₁ (A, C) and IgM (B, D) AFCs was measured by ELISPOT using NP₂₅-BSA and NP₅-BSA as the capture antigens. The levels of NP-specific serum IgG₁ (E) or IgM (F) antibodies were determined by ELISA. The data represent the mean ± the standard error (SE) from 5 individual mice in each group. Similar results were obtained from 2 independent experiments.