Independent and cooperative behavior of Thy1 and CD3:TcR T cell signalling pathways

Normal resting spleen T lymphocytes from mice were stimulated in vitro by monoclonal antibodies (mAbs) against either Thy 1 or CD3:TcR surface protein molecules. Although both mAbs were mitogenic, anti-Thy 1 activation generated 5 times more IL2 secretion than anti-CD3 activation under similar conditions. Production of IL3-like activity was comparable for both Thy1 and CD3-mediated activation. In addition, non-mitogenic doses of anti-CD3 and anti-Thy1 (0.16 micrograms/ml and 0.0125% ascites, respectively) mAbs induced T cell activation when provided together. These results indicate that Thy1 signalling cooperates with the CD3:TcR pathway to activate T cells. However, the Thy1 pathway is also regulated independently since IL2 production is larger when stimulated by anti-Thy1 than anti-CD3 mAbs.