Absence of MZ B-cell antibody response il2ra^−/− mice is restored in DKO mice. (A) Concentration of IgG1 and IgM in the serum of naive mice. Symbols represent individual mice. (B) Mice (n = 4/group) were immunized intravenously with 10⁸ colony forming units of heat-inactivated S pneumoniae. Blood was collected before and 5 days after immunization. Serum IgM antibody titers specific for phosphorylcholine were determined by ELISA. (C) Mice (n = 4/group) were immunized intravenously with Qβ-VLP and bled at day 14 for measurement of antibody responses. Qβ-specific IgM and IgG2a antibody titers were measured by ELISA. OD_405nm values show averages ± SEM of groups at indicated serum dilutions.