Direct effects of Corynebacterium parvum and BCG on human monocyte-mediated tumour cell cytostasis in vitro

Four strains of Corynebacterium parvum (Cp) and BCG induced low levels of cytostatic ability to a human tumour cell line in human monocytes when added directly to conventional monocyte cultures. The cytostatic ability induced by mediators from autologous lymphocytes stimulated with the same agents was greater than that produced by direct addition to monocytes. BCG was more efficient in stimulating lymphocyte DNA-synthesis and lymphokine release than any of the Cp strains tested. In order to test the influence of contaminating adherent lymphocytes on the direct induction of cytostasis, monocyte cultures of greater than 99.9% purity were prepared by adherence purification. Cp induced low levels of cytostatic ability in such highly purified monocytes when added directly to the monocytes. Addition of BCG and Candida albicans had an adverse effect on the cytostatic ability of purified monocytes. A morphological study of Cp interaction with purified monocytes was performed. Cp, but not BCG, would seem to be able to induce low levels of cytostatic ability in human monocytes without lympohcyte cooperation. Human monocyte activation by the more effective lymphokine pathway is more efficiently triggered in vitro by BCG than by Cp.