In vivo challenges. A, Stimulation index of Pneumovax-specific IgM calculated as the ratio of IgM produced at day 21 after vaccination and before immunization. B, Correlation between stimulation index of Pneumovax-specific IgM and absolute count of splenic B cells in BMT WT (solid circles), BMT OS (open circles), and GT 2.6kbUCOE (squares) mice. The Spearman r value is indicated. C, Stimulation index of TNP-KLH–specific IgM calculated as the ratio of IgM produced 21 days after immunization and before immunization. D, Stimulation index of TNP-KLH–specific IgG calculated as the ratio of specific IgG produced at day 28 and before the boosting dose. E, Correlation between the stimulation index of TNP-KLH–specific IgG and absolute count of splenic B (left) or T (right) cells. The Spearman r value is indicated for each graph. Statistical significance was determined by using nonparametric 1-way ANOVA with the Dunn posttest (Fig 5, A, C, and D) or by using Spearman correlation (Fig 5, B and E). *P < .05 and ***P < .001. All data show means 6 SDs.