Relationship between non-specific activity of macrophages and immune responses to Listeria monocytogenes.

Delayed footpad reactions and acquired cellular resistance to Listeria monocytogenes were studied in mice whose mononuclear phagocyte system (MPS) had been blocked or stimulated. Colloidal carbon was used for the blockade of MPS and Corynebacterium parvum used for the stimulation. Strong delayed footpad reactions. On the other hand, the i.v. injection of 3 X 10(1) listeria induced an appreciable level mice, while in MPS-stimulated mice, i.v. injection with even 4 X 10(3) listeria could not induce such strong delayed footpad reaction. On the other hand, the i.v. injection of 3 X 10(1) listeria induced an appreciable level of delayed footpad reaction only in MPS-blocked mice. Acquired cellular resistance was depressed by MPS stimulation, whereas it was augmented by MPS blockade. These results suggested that non-specific activity of MPS modulates subsequent immune responses after inoculation of listeria.