HIGH CD30 LIGAND EXPRESSION BY EPITHELIAL-CELLS AND HASSALS CORPUSCLES IN THE MEDULLA OF HUMAN THYMUS

CD30 is a member of tumor necrosis factor (TNF) receptor superfamily t hat is expressed by activated T cells in the presence of interleukin-4 (IL-4). Although CD30 can mediate a variety of signals, CD30-deficien t mice have impaired negative selection of T cells, suggesting that at least in the context of murine thymus, CD30 is a cell death-mediating molecule. The ligand for CD30 (CD30L) is a membrane-associated glycop rotein related to TNF, which is known to be expressed mainly by activa ted T cells and other leukocytes. However, the nature of CD30L-express ing cells involved in the interaction with CD30+ thymocytes is unclear . We report here that in postnatal human thymus the great majority of CD30+ cells are double positive (CD4+CD8+), activated, IL-4 receptor-e xpressing T cells which selectively localize in the medullary areas. M oreover, many medullary epithelial cells and Hassal's corpuscles in th e same thymus specimens showed unusually high expression of CD30L in c omparison with other lymphoid or nonlymphoid tissues. These findings p rovide additional information on the nature and localization of CD30thymocytes and show that epithelial cells are the major holder of CD30 L in the thymic medulla. (C) 1998 by The American Society of Hematolog y.