Anti-Thy-1-induced proliferation of immature thymocytes expressing the CD3-associated gamma/delta heterodimer.

A series of rat monoclonal antibodies (mAb) directed against the Thy-1 molecule have been evaluated for their ability to stimulate immature (CD4-8-) murine thymocytes. CD4-8- thymocytes could be induced to proliferate by several anti-Thy-1 mAb provided that exogenous interleukin 1 or interleukin 2 was provided. Apparently non-stimulatory anti-Thy-1 mAb could be rendered stimulatory if cross-linked by a rabbit anti-rat immunoglobulin reagent. Anti-Thy-1-stimulated CD4-8- thymocytes were found to uniformly express CD3 but did not stain positively with F23.1, a mAb reactive with alpha/beta T cell receptors utilizing the V beta 8 gene family. Immunoprecipitation analysis of such stimulated CD4-8- thymocytes indicated that they expressed a CD3-associated heterodimer of 45 kDa/35 kDa most likely corresponding to the product of the gamma and (putative) delta T cell receptor genes. Taken together, these data demonstrate that anti-Thy-1 mAb selectively activate a subset of CD4-8- thymocytes committed to the gamma/delta T cell receptor lineage.