Thymocyte differentiation from lentivirus-marked CD34(+) cells in infant and adult human thymus

Changes in thymic function and immune system homeostasis associated with HI V infection or chemotherapy have significant effects on the ability of pati ents to maintain a complete T cell receptor repertoire. Therefore, the deve lopment of in vitro systems to evaluate thymic function in children and adu lts may aid in the understanding of thymopoiesis and the development of new therapies to improve thymic output. Here we use a lentivirus-based gene tr ansfer system to mark CD34(+) cells with EGFP and follow their differentiat ion into CD4(+) and CD8(+) single positive thymocytes in human thymic organ cultures. Lentivirus-marked cells entered the thymus and were detected in both the cortex and medulla. Pretreatment of the thymus with a-deoxyguanosi ne depleted resident thymocytes and significantly increased the percentage of EGFP(+) thymocytes. High frequency gene transfer into CD34(+) cells and maintained expression throughout differentiation allows for the in vitro as sessment of thymic function. In thymuses ranging in age from fetal to adult we observed EGFP(+) thymocytes at all stages of development suggesting tha t thymuses of all ages are capable of accepting new T cell progenitors and contributing ro the maintenance of T cell homeostasis. (C) 2000 Elsevier Sc ience B.V. All rights reserved.