EFFECTS OF NEONATAL THYMECTOMY AND THYMUS GRAFT RESTORATION ON ALLOANTIGEN AND PHA STIMULATION OF WItOLE AND GRADIENT-SEPARATED SUB- :POPULATIONS OF SPLEEN CELLS

The thymus is influential in establishing and mainta ining elements of immune function throughout life (1, 2) and appears to be required for elicitation of delayed hypersens i t iv i ty reactions, for effective rejection of allografts (3, 4), for resistance to tumor induction (5, 6), and for response to certain classes of antigens (7, 8). The objective of the studies to be reported here was to examine further the role of the thymus in cellular recognition. The susceptibi l i ty of whole and albumin gradient-separated subpopulat ions of cells t aken from mice thymectomized at b i r th to s t imulat ion in vi t ro by alloantigens and P H A was assayed. The capaci ty of thymus grafts of differing origins to restore cellular react iv i ty was also explored. These studies confirm tha t the thymus is required for normal levels of responsiveness of lymphoid cells to p r imary s t imulat ion in vi t ro by alloantigens and PHA.