Murine leukaemogenesis: monoclonal antibodies to T-cell determinants arrest T-lymphoma cell proliferation

We have proposed a receptor-mediated leukaemogenesis hypothesis wherein T lymphomas would be clones of T cells bearing mitogen-linked surface receptors specific for the envelope determinants of the inducing MuLV. A prediction of the hypothesis is that T-lymphoma proliferation is dependent on continued presentation of MuLV envelope determinants to these cell-surface receptors, and that substances which interfere with receptor-virus interactions should inhibit T-lymphoma proliferation. Rat monoclonal antibodies were raised to the AKR mouse T lymphoma KKT-2, and these antibodies were screened independently for blockade of virus-binding and for cytostatic activity on KKT-2 cells. We report here that those monoclonal antibodies which block virus binding inhibit growth of KKT-2 cells in vitro, whereas monoclonal antibodies which bind to these cells but do not block virus binding are not cytostatic. Three of the four cytostatic antibodies detect determinants on the Thy-1 molecule, while none of the other (noncytostatic) antibodies detect Thy-1. Antibody inhibition of KKT-2 cell growth is precluded by saturation of KKT-2 virus receptors with the inducing leukaemia virus.