Genetic limits of thymic immunosuppression of anti-hapten antibody production in Xenopus laevis laevis, the South African clawed toad.

Thymic immunosuppression in adult Xenopus laevis laevis, the South African clawed toad, is antigen-dependent and antigen-specific, but it is not genetically restricted. In this report, we show that combination in vitro with a thymus from an immunized Xenopus laevis laevis can suppress antibody production to a hapten from spleen fragments, if the spleen fragments are derived from a subspecies of Xenopus laevis or a species of Xenopus which shares the same diploid chromosome number (2N = 36). Some aspects of the evolution of thymic immunosuppression are considered in the light of these results.