Depression of protective mechanisms against microörganisms in tumor-bearing mice and its restoration by adjuvants.

Bacterial growth within 72 hr after an intravenous inoculation with Listeria monocytogenes was enhanced strikingly in the liver of mice, when viable cells of sarcoma-180 were injected subcutaneously into ddN, C3H/He, and BALB/c mice 5 hr before the inoculation. Such an enhanced bacterial growth appears to be attributable to a depressed ability of macrophages to digest engulfed bacteria. Pretreatments with zymosan, killed BCG, or viable BCG prevented such depression in tumor-bearing mice and increased the bactericidal activity in the liver of normal and tumor-bearing mice above the level of non-treated normal mice. Such adjuvants may be useful not only for augmentation of antitumor activity but also for augmentation of antimicrobial activity in tumor-bearing hosts.