Glce^−/− mice have reduced basal serum Ig levels, an attenuated antigen-dependent immune response, and reduced plasma cell numbers. (A) Serum Ig concentrations in nonimmunized Glce^+/+ and Glce^−/− mice. The concentration of Igs of different isotypes was measured by ELISA, preceding immunization with TNP-KLH. Bars represent the mean ± SD; n = 12. (B) The timeline of the immunization protocol. Glce^+/+ and Glce^−/− mice were immunized at 3 (primary, boost, reboost) subsequent time points (▿). Blood samples were taken and serum was isolated (▲). Mice were killed at 84 and 150 days () after primary immunization for analysis of the BM plasma cells. (C) TNP-specific antibody levels after immunization with TNP-KLH. ELISA was performed to measure the TNP-specific antibody titer of the IgM, IgG1, and IgG2b isotypes. ■ represents Glce^+/+ mice; and □, Glce^−/− mice. Outliers and nonresponders were statistically excluded. These graphs represent 3 independent experiments of at least 4 to 8 mice (mean ± SEM). (D) Number of BM plasma cells (day 84). Tissue sections of femurs obtained at autopsy were stained for κ-light chain to quantify the number of plasma cells per optic field (original magnification, × 40) (mean ± SEM; n = 4/group). (E) Number of BM plasma cells (day 150). Whole BM was isolated and BM plasma cells (B220⁻, syndecan-1⁺, Ly6c⁺) were quantified by FACS as percentage of total BM cells (mean ± SD, n = 4/group). (F) Total serum Ig concentrations in Glce^+/+ and Glce^−/− mice (day 49). The concentration of Igs of different isotypes was measured by ELISA after repeated immunization with TNP-KLH. Bars represent the mean ± SD; n = 12. *P < .05.