T-lymphocyte development and models of thymopoietic reconstitution

T-cell development occurs in the thymus and involves a complex stepwise differentiation process from hematopoietic progenitor cell through to the emergence of positively selected, non-self reactive naïve T cells, which emigrate from the organ into the blood stream. This process takes place in the three-dimensional context of a delicate latticework of thymic stromal cells, including epithelial-derived cells and dendritic cells that assist in the development of the mature T cell. The details of the steps in T-cell development are now more comprehensively understood and furthermore in vitro systems are in development to reiterate this process in vitro. The clinical impact of this work is clearly the understanding of immune reconstitution in immune compromised patients (e.g., those with HIV/AIDS or post transplantation) and the development of novel techniques for regenerating the spectrum of T-cell function in these individuals.