Corynebacterium parvum prevents immunization to admixed irradiated tumor cells by a local process.

Immunization of mice with 10(6) irradiated LSTRA murine leukemia cells (LX) induced weak immunity to subsequent tumor-cell challenge. Admixture of low doses (1.4-14 micrograms of C. parvum with the LX usually augmented the immunity. Higher doses (1,400-7,000 micrograms) of admixed C. parvum not only failed to augment immunity, but prevented immunization by the contained LX. We investigated the mechanism by which 1,400 micrograms of C. parvum mixed with 10(6) LX prevents immunization by the LX. The inhibitory effect was a function of the ratio of C. parvum to tumor cells. Injection of 1,400 micrograms C. parvum, alone or mixed with the LX, did not prevent immunization by LX given simultaneously at a separate site. Injection of C. parvum, alone or mixed with the LX, did not prevent immunization by LX injected simultaneously at a separate site sharing a common lymph-node drainage area. The high dose of C. parvum prolonged retention of radiolabelled LX at the injection site and decreased the rate of distribution of the LX to other organs, particularly the spleen. These results indicate that a high dose of C. parvum prevented immunization through a localized process at the injection site.