hAPRIL.01A blocks Peritoneal B1 B-cell expansion Eight- to 9-week-old mice (n = 5) were treated intraperitoneally once a week for 3 months with 100μg (in 100 μL of PBS) with the indicated proteins and subsequently analyzed for their lymphocyte composition in the peritoneal cavity. (A) Representative scatter plots in which Peritoneal Exudates Cells (PECs) of 5-month-old mice were stained for IgD (FITC) and CD43 (PE) to discriminate B1 and B2 B cells. T cells were gated out using CD3 (antigen-presenting cell). (B) Bar graph showing the average of B1 B-cell expansion (%B1/%B2). **P < .01, *P < .05, 1-way ANOVA.