THYMECTOMY: PROLONGATION OF IMMUNOLOGICAL TOLERANCE IN THE ADULT MOUSE.

The loss of acquired immunological tolerance of mice to bovine gamma globulin depended on the presence of the thymus. Mice were repeatedly injected with bovine gamma-globulin from birth until the age of 5 to 10 weeks and then thymectomized or sham operated. After 130 to 160 days without antigen, an accelerated (immune) disappearance of I(125) bovine gamma-globulin could be uniformly induced in controls while thymectomized mice remained tolerant. Adult thymectomized mice made tolerant by a single injection of bovine gamma-globulin lost tolerance more slowly than sham-operated controls.