A CD1d-dependent peripheral tolerance checkpoint limits GC B cell levels. (A) Schematic illustration of the experimental setup comparing GC entry after injections of apoptotic cells in mixed WT and CD1d^−/− BM chimeric mice. (B and C) Representative FACS gating of splenic GC B cells (GL7^hi and CD95^hi) from noninjected and injected mice of the indicated genetic background (WT = CD45.1⁺ and CD1d^−/− = CD45.1⁻). Data shown as percentage of B cells with GC phenotype of total B cells with the indicated genotype after two (D) or four (E) injections. Lines connect the CD1d^−/− and the WT populations in individual mice. n = 3–10. (F) Examination of the role of CD1d expression on GC B cell levels in Peyer’s patches in a mixed BM chimera, as in B and C. (G) Splenic GC B cells in WT and CD1d^−/− after the second injection of NP-OVA (see Fig. 1 G for protocol) measured by FACS. (H) FACS staining of CD1d expression on WT splenocytes injected four times with apoptotic cells. FoB, MZB, and GC cells gated as in Fig. 1 E and Fig. 4 C. Results are shown as individual mice and mean in F (n = 4) and H (n = 3–7) and mean ± SEM in G (n = 4–6). *, P < 0.05; **, P < 0.01. Data are representative of two independent experiments.