Fig. 2.

FtL-induced isotype switching in anti-FtL B-1a requires AID but occurs without T-cell help or GC support. (A) Live FtL-binding Igκ⁺ cells from spleen of C57BL6/J, TCRβ^−/−δ^−/−, and AID^−/− syngenic mice 5 d after FtL immunization were gated to reveal CD138 and IgG expression. Boxes show IgG⁺ CD138⁻ and IgG⁺CD138⁺ plasma cells. One of four experiments is shown. (B) AID and BCL6 expression in sorted anti-FtL B-1a (CD138^–) and anti-FtL plasma cells (CD138⁺) from spleen of day 5 FtL-primed C57BL6/J mice. Data for each gene is shown as fold-change relative to expression level (dashed line) in PerC B cells from nonimmunized mice. Each dot represents data for 100 sorted cells of each subset, n = 6. One of three experiments is shown.