Interactions entre les thymocytes et les cellules epitheliales de la medulla thymique. (interactions between thymocytes and thymic medullary epithelial cells.)

Direct lympho-stromal interactions constitutes an intrinsic part of T-cell differentiation. However the precise role of cellular complexes is far from clear. The objective of the present work was to gain an insight into this question. An in vitro model was previously developed in the laboratory, which detects the adherence of thymocytes to a thymic stromal cell line, E-5. Using this model, we describe here a novel lympho-stromal interaction involving L3T4$ sp+$/Ly-2$ sp+$ "cortical type" thymocytes and medullary epithelial cell. These adherent thymocytes appear at day 16 of murine gestation and their number vary during ontogenesis and leukemogenesis. After contact with epithelial cells, thymocytes become totally refractory to form further complexes, are activated and undergo some phenotypic modifications. All these results strongly suggest that this novel lympho-stromal interaction takes place in the transition of "cortical type" thymocytes into "medullary type" thymocytes