The effect of Fas^lpr on PtC-specific B cells. (A) Comparison of 6-1 and 6-1/Fas^lpr peritoneal B cells for liposome binding and CD43 and CD5 expression. Histograms are gated on CD19⁺ B cells. PtC-specific B-1 cells (CD43⁺ and CD5⁺) are boxed, and the percent of total CD19⁺ B cells is indicated. (B) The number, ± SEM, of PtC-specific B-1 cells present in the peritoneal cavity of 6-1 and 6-1/Fas^lpr between 1 and 6 months is graphed. PtC-specific B-1 cells were gated as shown in panel A. (C) Number, ± SEM, of IgM^a ASCs in wt and Fas^lpr recipient mice 2 weeks after transfer of 6-1 peritoneal cells.