In vitro models of T cell development

A number of in vitro systems are currently being used to study both thymocy te development and thymic stromal cell function. However, the usefulness of dispersed culture systems is limited since they often involve disruption o f interactions within the normal three-dimensional architecture of the thym us in vivo which are critical for normal development to proceed. In contras t, Fetal Thymus Organ Culture (FTOC) provides an experimental system where such interactions are maintained, thereby allowing in vitro access to key a spects of thymocyte development More recently, Reaggregate Thymus Organ Cul tures (RTOCs) have allowed detailed analysis of thymic stromal cell functio n, while retroviral transfection of thymocyte subsets under FTOC conditions provides a rapid means to investigate thymocyte development at the molecul ar level. Current use of the FTOC approach is summarised here, and where ap propriate is compared to the use of dispersed culture systems.