Suppression of glucocorticoid-induced thymocyte apoptosis by co-culture with thymic epithelial cells.

There are many reports concerning glucocorticoid-induced thymocyte apoptosis, but little is known about the participation of thymic stromal cells, especially the thymic epithelial (TE) cells, in the apoptosis. In this study, we investigated the in vitro effect of TE cells on dexamethasone-induced DNA fragmentation of thymocytes as a parameter for apoptosis. By co-culture of thymocytes with TE cell line, at the condition without cell-cell contact, the DNA fragmentation of thymocytes caused by physiological level of glucocorticoid was significantly suppressed. Same effect was detected when treated the thymocytes with the supernatant from the cultures of TE cell line. These results suggest that the humoral factors released from TE cells rescue the thymocytes from the glucocorticoid-induced apoptosis. Chemical and physico-chemical nature of the factors are discussed.