FIG 2.

Analysis of B1a and B1b cell subsets and NP-specific IgM responses in mice deficient in TACI, BAFFR, or BAFF. (A and B) Peritoneal cavity cells of mice were stained with antibodies specific for surface CD19, B220, IgM, CD23, Mac1, and CD5 and analyzed by flow cytometry. All cells were first identified as B1 cells (IgM⁺, CD19⁺ CD23⁻, and Mac1⁺ cells [plots not shown]). (A) The frequencies of B1a (CD5⁺) and B1b (CD5⁻) subsets among those B cells are shown. Five-percent contour plots are shown. (B) The numbers of B1a and B1b cells in the indicated mice are shown as means + standard deviations. These data were generated by analyzing a minimum of 20,000 cells and are representative of at least 4 mice from each indicated genotype. Differences between wild-type and mutant mice were determined using one-way ANOVA followed by Bonferroni's multiple comparison test. Data are representative of two independent experiments. (C) Wild-type (n = 5) and BAFFR^−/− (n = 7), TACI^−/− (n = 6), and BAFF^−/− (n = 7) mice were immunized intraperitoneally with 50 μg of NP-77 Ficoll. Blood samples were obtained on days 0, 7, and 14 postimmunization, and NP-specific IgM was determined by ELISA. The differences in antibody responses were analyzed by two-way ANOVA with Bonferroni's posttest (*, P < 0.05; **, P < 0.01; ***, P < 0.001). Data are representative of two independent experiments.