Thymus cell-cell interactions.

The recent advances in molecular biology and genetics, as well as the progress of in vitro techniques, have provided a more coherent image of the thymic function on the molecular level. But they have shifted the attention away from studies on the cellular level, which are necessary to clarify the biological roles of different cell types of the thymic microenvironment. The structure and function of the normal thymus depend on mutual interactions between thymocytes and nonlymphocyte cells. In this review a detailed description of morphological and phenotypic features of both maturing thymocytes and nonlymphocyte cells is given. The recent genetic and biochemical data are presented in conjunction with cytological results to enlighten the thymus cell-cell interactions during thymopoiesis and organization of thymic microstructure. Special emphasis is put on the experimental approaches, which may be used to study the interactions between thymocytes and nonlymphocyte cells in vivo.