Lack of an expansion of peritoneal B1b cells in B. hermsii-infected Cxcl13−/− mice. Peritoneal cells from naïve and convalescent-phase (at 35 days postinfection) wild-type and Cxcl13−/− mice were harvested and stained with monoclonal antibodies specific for IgM, CD23, CD5, and Mac1. The absolute cell counts of IgM+ B cells (A), B1b cells (IgM+ CD23− Mac1+ CD5−) (B), and B1a cells (IgM+ CD23− Mac1+ CD5+) (C) are shown. Data points represent cell counts from individual animals. Statistical significance was determined by a one-tailed unpaired Student's t test, with significance reached at a P of <0.05. n.s., differences not statistically significant.