Splenectomy impairs specific IgM in correlation with levels of IgM⁺IgD⁺CD27⁺ B cells. (A) IgM⁺IgD⁺CD27⁺ percentage of total B cells. (B) Serum IgM binding SP capsules and (C) PC. (D) S. pneumoniae cell wall, but not capsules, blocks binding of PC-specific IgM. (E) Serum IgM recognizing SP capsules and PC correlate with percentage of IgM⁺IgD⁺CD27⁺ B cells. Controls (□); splenectomized subjects (▪). P value represents the Spearman rank correlation test. Dotted line indicates 95% confidence interval. Control (n = 7); splenectomy (n = 21). Results derived from 1 of 2 replicate experiments. Bar represents mean; whiskers represent standard error of the mean. *P < .05, **P < .01.