Long-term survival and differentiation of human thymocytes in human thymus-grafted immunodeficient mice.

Thymus transplants have produced encouraging clinical outcomes in achieving thymopoiesis and T-cell development. This study was aimed to investigate whether human thymus contains self-renewing lymphoid progenitors capable of maintaining long-term T-cell development. Immunodeficient mice were transplanted with human thymic tissue along with autologous GFP-expressing or allogeneic CD34 cells and followed for human thymopoiesis and T-cell development from the thymic progenitors versus CD34 cells, which can be distinguished by GFP or HLA expression. In both models, long-term thymopoiesis and T-cell development from the thymic grafts were detected. In these mice, human thymic progenitor-derived T cells including CD45RACD31CD4 new thymic emigrants were persistently present in the periphery throughout the observation period (32 weeks). The results indicate that human thymus contains long-lived lymphoid progenitors that can maintain durable thymopoiesis and T-cell development.