Effects and mode of action of Corynebacterium parvum on murine tumour metastases.

The effects of Corynebacterium parvum (C. parvum) on Lewis lung tumour metastases have been studied. I.v. and i.p., but not s.c. C. parvum significantly reduced pulmonary metastases. When combined with excision of the primary tumour, C. parvum given not more than 2 days before caused slight reduction of metastases, but when given earlier, it caused significant reduction and some mice were cured. Metastases were increased by silica or cortisone acetate but were unaffected by trypan blue. The antimetastatic action of C. parvum was not altered by these treatments. Thymectomy and irradiation did not affect tumour metastases, or the antimetastatic action of C. parvum, whereas ALS depressed metastasis and abrogated the protective effects of C. parvum. It appears that the inhibitory effects of C. parvum on tumour metastases are mediated through macrophages in concert with a subpopulation of T2 lymphocytes.