AhR dampens both T cell–dependent and T cell–independent B cell responses. (A, left) Representative flow cytometry plot showing live singlet B220⁺ cells that are IgG1⁺ (top)- and B220⁺IgG1⁺NP-specific (bottom) in unimmunized (left), SRBC-immunized (middle), and NP-CGG–immunized (right) AhR^−/− mix chimeras at day 14. (Bottom right) Contribution of WT (CD45.1) and AhR^−/− (CD45.2) cells to the antigen-specific class-switched pool in NP-CGG–immunized AhR^−/− mix chimeras. (B) Quantification summary of percent contribution of WT (CD45.1) and AhR^−/− (CD45.2) cells to the splenic B220⁺IgG1⁺NP-specific pool on day 14 after NP-CGG immunization. (C) Representative flow cytometry plot showing IgG1⁺ B cells in the spleen and the percent contribution of WT (CD45.1) and AhR^−/− (CD45.2) to this pool in SRBC-immunized AhR mixed chimeras at day 14. (D) Quantification summary of percent contribution of WT (CD45.1) and AhR^−/− (CD45.2) cells to the B220⁺IgG1⁺ pool. (E) Quantification summary of percent contribution of WT (CD45.1) and AhR^−/− (CD45.2) cells to the B220⁺IgG1⁺NP-specific pool in AhR mixed chimeras immunized with T cell–independent type I (NP-Ficoll) or type II (NP-LPS) antigens at day 14. (F) Representative flow cytometry plot showing IgG1⁺ B cells in the spleen of SRBC-immunized AhR WT only chimera (WT→WT) and AhR KO only (hematopoietic KO; AhR^−/−→WT) mice. (G) Quantification summary of percent of B220⁺IgG1⁺ cells at day 14 after SRBC immunization of AhR WT only chimera (WT→WT) and AhR KO only (hematopoietic KO; AhR^−/− →WT) mice. (B, D, E, and G) n = 3. Mean ± SD is shown. *, P < 0.05; **, P < 0.005 (Student’s t test).