Monocytes and macrophages in malignant melanoma IV. Effects of C. parvum on monocyte function.

Assays for the capacity of peripheral-blood monocytes (a) to mature in vitro into macrophages, (b) to reduce nitro-blue tetrazolium (NBT) and (c) to lyse antibody-coated human Group A red cells, were applied to a group of 82 patients with histologically proven malignant melanoma. In patients with micrometastatic disease there was an enhancement of red-cell lysis and NBT reduction, suggesting that their monocytes are in some way "activated", whereas NBT reduction was suppressed in those with overt dissemination. Monocyte maturation in vitro was impaired in all patient groups to an extent which correlated with overall tumour burden. Corynebacterium parvum was administered i.v. to 12 patients with disseminated disease and by the intradermal route to 24 patients with micrometastatic disease. The 3 monocyte functions were significantly enhanced by C. parvum.