Immune cell distribution in spleens of 564+/+ mice. Spleen cell suspensions from 564+/+ (4 to 8 months), BXSB.Yaa (4 months), and B6 (4 months) mice were stained for different cell populations and analyzed by multicolor flow cytometry. Live single cells were gated and analyzed for B cells (B220+; A), follicular B cells (B220+CD5−CD23hiCD21lo/−; B), B1B cells (B220+CD5+; C), marginal zone B cells (B220+CD5−CD23lo/−CD21hi; D), germinal center B cells (B220+FAS+GL7+; E), and plasma cells (B220−CD138+; F). Each dot represents one animal. P values are determined by one-way analysis of variance with Tukey's multiple comparison test. Data are expressed as means ± SEM. ∗P < 0.05, ∗∗P < 0.01, ∗∗∗P < 0.001, and ∗∗∗∗P < 0.0001.