Basal serum immunoglobulin levels and immune responses in TAK1-deficient mice. (A) Basal serum immunoglobulin levels in TAK1-deficient mice. Basal serum levels of IgM, IgA, IgG1, IgG2a, IgG2b, and IgG3 in nonmanipulated CD19CreTak1^+/+ (n = 7) and CD19CreTak1^fl/fl (n = 9) mice were determined by ELISA. ―indicates mean values. (B,C) Immune response to TI-specific antigens in TAK1-deficient mice. CD19CreTak1^+/+ (n = 5) and CD19CreTak1^fl/fl (n = 5) mice were immunized intraperitoneally with the TI antigen, TNP-Ficoll. At 7 or 14 days after immunization, the titers of TNP-specific IgM (B) and IgG3 (C) in sera were determined by enzyme-linked immunosorbent assay (ELISA). ―indicates mean values. (D) Immune response to TD-specific antigens in TAK1-deficient mice. CD19CreTak1^+/+ (n = 8) and CD19CreTak1^fl/fl (n = 7) mice were immunized intraperitoneally with TD antigen, NP-CGG. Fourteen or 30 days after immunization, the titers of NP-specific IgG1 in sera were determined by ELISA. ―indicates mean values.