Antibody Responses to Hapten in Thymectomized Mice: Extraordinarily Pronounced Deficiency in IgG1 Production

Abstract

The effect of thymectomy on the production of antibodies was studied by immunizing mice with hapten-carrier conjugates. Antibody responses were analysed with monoclonal antibody-based quantitative isotype-resolving assays. In spite of bone marrow reconstitution, irradiation without thymectomy caused a long-lasting relative deficiency in responsiveness to T-independent antigens. Even when no visible remnants of the thymus could be observed at the autopsy of thymectomized mice, there appeared to be a gradual recovery of antibody-forming capacity within 4 months, as assessed by the response to a T-dependent antigen. Therefore, some of the thymectomized mice had to be regarded as having recovered with respect to the helper T-cell effect. The antibody responses to T-dependent antigens were improved in all isotypes by a functional T-cell system, but the IgG isotypes seemed to benefit more than IgM. The most conspicuous deficit in antibody production in non-recovered thymectomized mice was observed in the T-dependent responses of the IgG1 isotype (2000-fold reduction in contrast to about 50- to 100-fold in IgG2a, IgG2b, and IgG3).