To be or not to be: mutually antagonistic death signals regulate thymocyte apoptosis.

Recognition of self-antigens by immature thymocytes results in either activation-induced apoptosis (negative selection) or survival (positive selection). While it is believed that T cell receptor avidity plays a role in determining the outcome, the mechanisms responsible for this life or death decision are not known. Recent data concerning the mutual antagonism between activation- and glucocorticoid-induced apoptosis have prompted an examination of the potential interaction of these two signaling pathways in the regulation of antigen-specific selection.