Production of a monoclonal antibody inhibiting the killer activity

We established the hybridoma producing the monoclonal antibody (mAb) 3C3 by immunizing rats with mouse natural killer (NK)-like cells. The 3C3 mAb seemed to react mainly with T cells and T-lineage cell lines. The 3C3 antigen also seemed to be coincidentally expressed on a part of asialo GM1+ cells from nude mice, suggesting its expression on NK cells. Treatment of effector cells with 3C3 mAb markedly inhibited the killer activity against RL male-1 cells, but less so against YAC-1 cells, in vitro. It is suggested that the cell surface molecule defined by 3C3 mAb was closely associated with the killer activity of T cells and NK cells.