Neonatally induced tolerance to soluble protein antigens. II. A role for the thymus in prolonging tolerance

Mice were rendered tolerant to bovine serum albumin (BSA) or fowl γ-globulin (FGG) by neonatal injection. Spleen and thymus cells from tolerant mice were able to suppress responsiveness of normal adult spleen cells, but only if tolerant donor mice were between the ages of 6 weeks and the age at which mice were no longer tolerant (10 weeks for BSA tolerance and 20 weeks for FGG tolerance). To determine whether T-cell-dependent suppression was obligatory for the maintenance of tolerance, neonatal nude and euthymic littermate mice were injected with tolerizing doses of FGG. FGG-specific B-cell tolerance in nude mice lasted until the mice were 8 weeks of age. In sharp contrast, B-cell tolerance in euthymic littermates lasted until 22 weeks of age. These results are consistent with a “fail-safe” role of T-cell-dependent immune suppression in the maintenance of tolerance.