An in vitro technique for detecting anti-tumour responses was studied and shown to involve non- T cells. Further examination of the effector mechanism revealed that tumour inhibition was antibody mediated, probably through complement dependent lysis; ADCC was considered unlikely. The amount of antibody involved was small, as shown by indirect immunofluorescence labelling of tumour cells, but was nevertheless effective in vitro and in causing regression of tumours in vivo. These findings may have important implications for the manipulation of the host responses to tumours
