Critical role of the thymus in establishing humoral immunity in amphibians: Studies on Xenopus thymectomized in larval and adult life

Proliferative studies on spleen lymphocytes suggest the absence of induced cellular activity to sheep erythrocytes in Xenopus thymectomized at 7 days of age. Immunological studies (measurement of splenic rosette-forming and plaque-forming cells and serum haemolysins) show that throughout larval life the thymus plays a critical role in establishing reactivity to red cells, since thymectomy as late as 40 days (stage 57) impairs the antibody response. In contrast, thymectomy during metamorphosis or in early adult life has no apparent debilitating effect.