Figure 4.

T cell-dependent anti-NP responses. (A) Comparison of the day 12 IgG1^a anti-NP response to NP-CG immunization in mice in which one IgH allele was of b allotype (derived from C57BL/6) and the other was either wild type a allotype (derived from 129; a-μ_s⁺), a allotype but carrying the targeted μ_s deletion (a-μ_s⁻), or b allotype (b). These mice (sets of four) were derived from breeding the ES cell-derived chimeras against C57BL/6. The solid section at the base of each histogram depicts the prebleed titer. The titers are given in arbitrary units as detailed under Materials and Methods. (B) Comparison of the day 12 total IgG1 anti-NP response to NP-CG immunization in 129 and C57BL/6 mice. (C) Comparison of the titers of IgG1 anti-NP antibody in μ_s^−/− (open symbols) and wild-type mice (solid symbols) immunized with soluble NP-KLH and boosted (arrow) on day 24 as measured by ELISA on NP₃₀-BSA-coated plates. Tail bleeds were obtained on the days indicated on the x axis. (D) Titers of IgG1 anti-NP antibody 12 days after NP-KLH immunization were compared in μ_s^−/− and control mice in which the antigen challenge had been given together with pooled serum IgM from unprimed mice (an amount equivalent to the IgM present in 0.5 ml of serum). (E) Comparison of the titers of IgG1 anti-NP antibody in μ_s^−/− (open symbols) and control littermates (solid symbols) immunized with alum-precipitated NP-CG and boosted (day 26) as monitored by ELISA on NP_2.5-BSA-coated plates. (The magnitude of the day 12 IgG1 anti-NP response in NP₁₃-CG immunized control mice is about 8-fold greater than in NP₁₃-KLH mice when both are compared on NP₃₀-BSA coated plates.) (F) Comparison of the titers of IgG1 anti-NP antibody in the day 12 serum of the NP₁₃-CG immunized mice as assayed plates coated with NP_2.5-BSA and NP₃₀-BSA. (G) Analysis by surface plasmon resonance of the binding of serum antibody to NP₆-BSA immobilized on the chip. The serum samples were obtained from μ_s^−/− and μ_s^+/+ siblings 12 days after challenge with NP-CG, and the 7S Ig fraction was purified as described in Materials and Methods. The bulk of the antibody in the μ_s⁻ sample that is bound initially to the chip clearly has a dissociation rate severalfold higher than that in the control, although the heterogeneity of the serum antibody and resultant complexity of the dissociation curves preclude a simple calculation of k_off. (H) Germinal centers in the spleens of μ_s^−/− mice 12 days post-NP-CG immunization were visualized by staining for peanut agglutinin.