The anti-inflammatory agent sodium aurothiomalate appears to act upon mononuclear phagocytes, inhibiting their lysosomal enzyme activity. Evidence is presented that gold salts can increase the number of lung tumour nodules that develop following intravenous injection of tumour cells and pretreatment can enhance the take of a subcutaneous tumour inoculum. In contrast, they do not affect the later growth of tumour. Gold salts can also suppress the action of systemically administered C. parvum in inhibiting the growth of subcutaneous tumours. These results are taken as supporting the evidence in favour of a fast acting nonspecific anti-tumour mechanism, probably macrophage mediated, that can be inhibited by gold salts and enhanced by C. parvum. The effect of gold salts upon other biological changes induced by C. parvum is examined, including its adjuvant action, and the results are discussed in the context of the mechanisms underlying the immunotherapeutic action of this organism
