IMMUNOLOGIC TOLERANCE IN THYMECTOMIZED, IRRADIATED RATS GRAFTED WITH THYMUS FROM TOLERANT DONORS.

Lewis rats, thymectomized at 5 weeks of age and irradiated at 8 weeks, received grafts of adult thymus and marrow, one or both grafts being derived from donors tolerant to bovine gamma-globulin. Challenge 3 or 6 weeks after grafting showed that delayed sensitization could not be induced in animals which received a tolerant thymus or tolerant thymus and marrow, though sensitization to a heterologous antigen (chicken ovalbumin) occurred normally. Arthus reactivity was regained slowly in animals receiving normal thymus and marrow and, to an equal extent, in those receiving grafts from tolerant donors.