ICAM-1-INDEPENDENT, ICAM-2-INDEPENDENT AND LFA-1-INDEPENDENT HOMOTYPIC T-CELL AGGREGATION INDUCED BY A NOVEL ACTIVATING MONOCLONAL-ANTIBODYTARGETING THE MURINE THY-1 MOLECULE

We have previously reported that the murine T cell line EL-4 has an ag gregating phenotype, displaying homotypic aggregation (HTA) when expos ed to monoclonal antibodies targeting specific cell surface molecules such as leukocyte function-associated antigen-1 (LFA-1). We have used this property of EL-4 cells to isolate additional HTA-inducing MAb by screening a panel of hybridomas that were generated from rats immunize d with EL-4 cells. We have isolated a novel anti-Thy-1 MAb (termed FF- 10) that is a powerful inducer of HTA in EL-4 cells. In addition to in duction of HTA, FF-10 also induces splenocyte proliferation but inhibi ts anti-CD3-driven T cell proliferation. Thy-1-induced HTA cannot be b locked with MAb targeting intercellular adhesion molecule-1 and -2 (IC AM-1, ICAM-2) or LFA-1. Thus, the FF-10 MAb represents a novel and uni que tool to investigate the diverse roles of the murine Thy-1 molecule in T cell activation, proliferation and apoptosis.