Splenic B cells were purified from wild type (white bars) and RP105−/− mice (black bars) mice, transferred into μMT (B cell deficient, RP105+/+) mice, and allowed to reconstitute for 8 wks. (a) Following engraftment, MZ B and FO B cell subsets were quantified by flow cytometry. (b) B cell proliferative responses were quantified by thymidine incorporation. Means +/− SE are depicted. N=12–15 mice/genotype, pooled from 3 independent experiments. NS (not significant; unpaired, two-tailed t test).