Responsiveness of senescent mice to the antitumor properties of Corynebacterium parvum.

The antitumor properties of Corynebacterium parvum have been studied in young (3- to 8-month-old) and aged 18 or more months old) BALB/c mice given s.c., i.m., i.p., or i.v. transplants of the highly malignant, weakly immunogenic line 1 lung carcinoma, and in aged (25- to 33-month-old) BALB/c mice bearing primary mammary tumors. These aged BALB/c mice were shown to be less immunoresponsive than their younger counterparts, and this, in combination with nonimmunological factors, made them more sensitive to the lethal effects of the line 1 carcinoma. Correspondingly, C. parvum proved to have less antitumor activity in aged mice than it did in young mice. In spite of this relatively weaker antitumor activity for C. parvum in aged mice, repeated injections of this agent were able to induce temporary regressions of the primary mammary tumors studied and therby prolong survival time.