Inhibition of macrophage chemotaxis by supernatant fluid from malignant cell lines.

The chemotactic locomotion of peritoneal macrophages in vitro was measured in the presence of supernatant fluid from 27 different tumour cell lines. All the tumour-derived cells tested caused profound depression of macrophage chemotaxis towards the chemo-attractant casein. Conversely, supernates from rapidly dividing non-malignant cells uniformly failed to depress macrophage migration. This confirms the results of a previous investigation and provides further evidence that malignant tumours depress the functions of the reticuloendothelial system of the host animal in vivo.