PHENOTYPIC AND IMMUNOHISTOLOGICAL ANALYSES OF THE HUMAN ADULT THYMUS - EVIDENCE FOR AN ACTIVE THYMUS DURING ADULT LIFE

We analyzed cellular content of thymic samples from 26 human healthy d onors, ranging from 1 week postnatal to 49 years old. Our results show ed that there was an overall decrease in cellular density, beginning e arly during life, but with two peaks of cellular density, at 9 months and 10 years of age. Histological and immunohistological analyses show ed that variations in cellular density were correlated with the morpho logical changes observed during thymic involution, namely the enlargem ent of interlobular trabeculae and the development of adipocytic tissu e. However, the adult thymus still contained thymocytes, up to 49 year s. Phenotypic analysis showed no significant variations according to t he age of donors in the distribution of the main thymocyte subsets, bo th precursors and more mature cells. These results suggest that the hu man thymus remains active during adult life. (C) 1997 Academic Press.