In Vitro Responses of Rat Lymphocytes Following Adult Thymectomy

Abstract

Inbred DA rats thymectomized at 8 weeks of age showed a marked decrease in in vitro reactivity of spleen cells to phytohemagglutinin-P (PHA) and concanavalin-A, appearing as early as 3 days and vanishing by 35 to 40 days. This change could not be explained by enlargement of the spleen. However, there was a proliferation of blasts in the splenic marginal zones at 1 to 2 weeks, but not at other times. Peripheral (popliteal, inguinal, and axillary) and mesenteric lymph nodes showed a similar effect. This effect was of lesser magnitude and appeared only 20 days after thymectomy, with recovery at the same time as the spleen, and was not observed in rats thymectomized at 4 weeks of age. Spleen cells after thymectomy showed a relatively inconstant decrease in reactivity to hemiallogeneic cells, while the decrease with both types of lymph node cells was, if anything, greater than the decrease in PHA reactivity. The evidence suggested that these findings could not be simply attributed to loss of a putative thymus-derived lymphocyte subpopulation.