(a) Mice were challenged i.p. with LPS (40 μg), and splenic B cell proliferation was quantified by BrdU incorporation 48 h later. Means +/− SE are depicted; N=10 mice/genotype, pooled from 2 independent experiments. *P<0.005; unpaired, two-tailed t test. (b) FACS-sorted MZ B cells were stimulated as indicated, and proliferation was quantified by thymidine incorporation. Means +/− SE of triplicate cultures are depicted; N=4 pooled mice/genotype; representative of 2 separate experiments. *P<0.0001, unpaired, two-tailed t test.