ERK5 is dispensable for B cell antibody responses to TD and TI antigens. (A) mb1-cre⁺ erk5^fl/fl mice and mb1-cre⁺ erk5^wt/wt control mice were immunized with NP₂₇-CGG alum or PBS alum controls. α-NP IgM (left) and α-NP IgG1 (middle) serum antibody levels were quantified by ELISA (mean ± SEM; a.u., arbitrary units), 14 days after NP₂₇-CGG immunization. The right panel represents splenic α−NP IgG1⁺ GC B cells 14d after NP₂₇-CGG immunization (mean absolute number ± SEM). (B and C) mb1-cre⁺ erk5^fl/fl mice and mb1-cre⁺ erk5^wt/wt control mice were immunized with TNP-LPS (B) or TNP-Ficoll (C) and bled at the indicated time points. (B) α-TNP IgM (left), α-TNP IgG3 (middle) and α-TNP IgG2b (right) serum antibody levels were quantified by ELISA (mean ± SEM; a.u., arbitrary units). (C) α-TNP IgM (left), α-TNP IgG1 (middle), and α-TNP IgG2b (right) serum antibody levels were quantified by ELISA (mean ± SEM; a.u., arbitrary units). All results are representative of two independent experiments (at least four independent mice per genotype each).