Fig. 3.

FtL immunization induces splenic anti-FtL B-1a responses in IL-7^−/− mice. Live splenic CD19⁺ B cells from IL-7^−/− mice injected with PBS or immunized with FtL for 3–4 d were gated to reveal FtL-binding Igκ⁺ B cells (“diagonal” in circled population, Upper), and further gated to distinguish anti-FtL plasma cells (CD138⁺CD5^–) (boxed population, Lower) from CD138^– cells, >95% of which are CD5⁺. (For serum responses, see Fig. S3C).