Suppression of host resistance against Listeria monocytogenes infection by 15-deoxyspergualin in mice.

The effects of 15-deoxyspergualin (DSG), an immunosuppressive agent, on host resistance against Listeria monocytogenes were studied in mice. Administration of DSG in the early phase of infection resulted in fatal listeriosis by preventing acquired anti-listerial resistance, even though the infectious dose was sublethal for the untreated controls. In contrast, DSG treatment started after development of the acquired immunity was ineffective. Endogenous production of interferon-gamma (IFN-gamma) and tumour necrosis factor (TNF) in the bloodstreams induced by the infection was normal in DSG-treated mice. Nevertheless, augmentation of macrophage functions such as expression of major histocompatibility complex (MHC) class II antigens, phagocytic activity and listericidal activity induced by the infection was abrogated by DSG treatment. These results suggest that the inhibitory effect of DSG on anti-listerial resistance might be different from cyclosporine A (CsA).