Transplantation of cultured thymus fragments. III. Induction of allotolerance.

Balb/c nude mice were transplanted with cultured thymic fragments from C57BL/6, hybrid (C57BL/6xC3H F1 or BALB/cxC3H F1) or 2 separate strains simultaneously. Tolerance to H-2 of the thymus donor strain(s) was assessed by skin-graft acceptance and was seen in all cases except where 2 thymuses, each of differing strains, were transplanted simultaneously. Examination of mixed leukocyte culture and cell mediated lympholysis revealed blunted reactivity against thymus donor strains when skin graft tolerance was seen. Demonstration of a suppressor cell population was unsuccessful although a decreased cytotoxic T-cell potential was suggested by decreased GVH activity. These studies showed a unique dependence upon the thymus gland for the phenomenon demonstrated and are taken to be an example of a more generalized process in which effector cell function of the thymus is controlled by intrathymic events during the early maturation of precursor effector cells.