Alterations in thymopoiesis in intact and peripubertally orchidectomized adult rats of different age

In adult rats 3, 6 and 9 months post-orchidectomy performed at the age of 30 days the thymus weight, thymocyte yield and relative proportions of thymocyte subsets (delineated by expression of CD4/CD8 molecules and TCRalphabeta) were analyzed in order to elucidate a putative role of male gonadal hormones in the shaping of thymus size and intrathymic T cell Maturation, In 4-month-old control rats the thymus size and cellularity returned to the corresponding levels in 1-month-old rats, These levels were sustained during the following 6 months. In spite of that, the distribution of the main thymocyte subsets in these rats as Subjected to significant changes, probably due to an age-associated diminishing thymus ability to provide efficient T cell differentiation. The results added further v.,eight to a potential feedback regulatory role of CD4+8- cells in thymopoiesis. Furthermore. they revealed that the orchidectomy-induced (i) enlargement of the thymus size and enrichment of the thymic lymphoid cell content are of a limited duration and (ii) alterations in the relative proportion of thymocytes become quantitatively more pronounced with duration of the gonadal deprivation. Thus, the study also indicates that the age-associated changes in gonadal hormones may be, at least partly. responsible For the age-related reshaping a of the T cell maturation sequence, and hence for remodeling T cell dependent immune functions