Role of the Ly 1 antigen in interleukin 1-induced thymocyte activation

Abstract

Interleukin 1 (IL 1), but not IL 2-induced thymocyte proliferation was augmented by monoclonal antibodies (mAb) against the Ly 1 antigen. The anti-Ly 1 mAb could also co-stimulate thymocytes with phytohemagglutinin (PHA) alone, mimicking the effect of IL 1. Moreover, overnight culture with PHA of thymocytes, but not of spleen T lymphocytes led to selectively enhanced expression of the Ly 1 antigen on the cell surface. Similar data were generated at the clonal level. Thus, a thymocyte hybridoma (22A6) could be stimulated to release IL 2 in response to PHA plus IL 1, but also to PHA plus anti-Ly 1 mAb. In addition, 22A6 exhibited enhanced cell surface expression of the Ly 1 antigen after overnight culture with PHA. These data suggest a critical role for the Ly 1 antigen in thymocyte proliferation, perhaps by serving as an IL 1-receptor.