A Cellular Component of Thymic Function

THYMECTOMY in the new-born 1,2 or in the adult irradiated mouse 3 leads to a long-lasting suppression of the ability to respond to primary antigenic challenge. It has been shown in both instances that thymus grafting is effective in restoring immunological competence 2,4,5 and, furthermore, when using a cytologically marked thymic graft, it has been possible to detect cells derived from the graft in the spleen and lymph nodes 2,5 . It has, therefore, been suggested 5 that it may be these donor cells which are directly responsible for the recovery of the primary immune response in thymus-grafted animals.