Alterations of host resistance to Listeria monocytogenes in tumour-bearing mice and the effect of Corynebacterium parvum.

In tumour (fibrosarcoma)-inoculated mice, alterations of host resistance to Listeria monocytogenes following tumour growth were examined. Non-immune macrophage-mediated antibacterial resistance was severely suppressed up to day 4 or so after tumour inoculation, but was enhanced thereafter. On the other hand, T cell-mediated immune resistance retained the control level up to day 7 or so, but was suppressed thereafter. Suppression of macrophage-mediated antibacterial resistance was not observed if the tumour-bearing mice had been pretreated with Corynebacterium parvum. Moreover, this suppression of macrophage-mediated resistance was attributable to the presence of a serum factor that interferes with the function of free macrophages but not with that of resident macrophages. The ability of this serum factor to suppress macrophage-mediated antibacterial resistance, however, was not reduced by C. parvum administration.