In Vitro Binding of L3T4−Lyt-2− Pgp-1+ Thymocytes to Thymic Accessory Cells
Thymic macrophages and dendritic cells (MØ-DC) have been found to play an important role in the regulation of thymocyte maturation. It has for instance been suggested that thymic MØ-DC are involved in the induction of tolerance (1,2), regulation of la expression on cortical epithelial cells (3) and in the stimulation of thymocyte and prothymocyte proliferation (4,5). The events regulating these maturational effects may require cell-cell contact. Indeed multicellular complexes of thymocytes and MØ-DC have been described (6). We recently described an in vitro model to study the direct interaction between thymocytes and the phagocytic cells of the thymic reticulum (P-TR) (7), which leads to complement receptor type 3-mediated rosette formation (8). Rosetting thymocytes were found to show higher responsiveness and IL-2 receptor expression during T-cell mitogen (Con A) stimulation than did non rosetting thymocytes (9). It was also found that the rosetting thymocytes have a greater capacity for migrating back to the thymus after transfer into irradiated congeneic mice (El Rouby, Ezine and Papiernik, 1978, submitted). We analysed the phenotype of the rosetting thymocytes and in the present communication we show that the rosetting cells contain a small subset of L3T4−Lyt-2− double negative (DN) cells. These binding DN thymocytes are enriched in cells expressing Pgp-1 antigen.
KeywordsDouble Negative Rosette Formation Fetal Thymus Rosetting Cell Adult Thymus
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