A NOVEL TYPE OF CELL-DEATH OF LYMPHOCYTES INDUCED BY A MONOCLONAL-ANTIBODY WITHOUT PARTICIPATION OF COMPLEMENT

A monoclonal antibody, RE2, raised by immunizing a rat with cell lysat e of a mouse T cell clone, was found to directly kill interleukin 2-de pendent T cell clones without participation of serum complement. Fab f ragments of RE2 had no cytolytic activity, while the cross-linking of Fab fragments with anti-rat immunoglobulin reconstituted the cytotoxic ity. The cytotoxicity was temperature dependent: the antibody could ki ll target cells at 37 degrees C but not at 0 degrees C. Sodium azide, ethylenediaminetetraacetic acid, and forskolin did not affect the cyto lytic activity of RE2, while the treatment of target cells with cytoch alasin B and D completely blocked the activity. This suggested that th e cell death involves a cytoskeleton-dependent active process Giant ho les on the cell membrane were formed within 5 minutes after the treatm ent with RE2, as observed by scanning electron microscopy. There was n o indication of DNA fragmentation nor swelling of mitochondria during the cytolysis, suggesting that the cell death is neither apoptosis nor typical necrosis. The antibody also killed T cell lymphomas and T and B cell hybridomas only when these cells were preactivated with concan avalin A, lipopolysaccharide, or phorbol myristate acetate. Preactivat ed peripheral T and B cells were sensitive to the cytotoxicity of RE2, while resting T and B cells were insensitive. These results provide e vidence for a novel pathway of cell death of activated lymphocytes by membrane excitation.