Enhanced antibacterial resistance in neutropenic mice treated with human recombinant interleukin-1 beta.

Human Recombinant IL-1 was investigated for its ability to increase non-specific resistance to Staphylococcus aureus in neutropenic mice. Mice, rendered neutropenic with cyclophosphamide and then administered IL-1 intraperitoneally, demonstrated enhanced resistance to subsequent challenge with S. aureus as measured by increased survival and bacterial clearance. No protective effects were observed with heat inactivated IL-1. Efficacy was observed only when both IL-1 and the subsequent bacterial challenge were administered into the same site. Despite the observed protective effects, animals treated with IL-1 did not have increased numbers of blood leukocytes or peritoneal phagocytes prior to infection or at the times coincident with bacterial clearance. Based upon these observations, enhanced activity of resident macrophages may be responsible for the protective effects observed in IL-1 treated mice.