A role for IL-1 alpha in inducing pathologic inflammation during bacterial infection.

Infection with pathogenic microbes often results in a significant inflammatory response. A cascade of proinflammatory cytokines including tumor necrosis factor alpha (TNF-alpha) and IL-1 initiates this response. Although there is a clear role for IL-1 during infection, little is known to distinguish the role of IL-1 alpha from that of IL-1 beta during this process. With the use of Yersinia enterocolitica as a model enteric pathogen, we have identified a specific role for IL-1 alpha in inducing pathologic inflammation during bacterial infection. Depletion of IL-1 alpha in mice infected with wild-type Y. enterocolitica results in significantly decreased intestinal inflammation. Furthermore, a bacterial mutant that does not induce IL-1 alpha expression but induces normal levels of IL-1 beta, TNF-alpha, and IFN-gamma, causes greatly reduced intestinal inflammation and is attenuated by LD(50) analysis in the C57BL/6 mouse model. These results demonstrate a distinct and unrecognized role for IL-1 alpha in inducing intestinal inflammation that cannot be compensated for by the endogenous levels of IL-1 beta, TNF-alpha, or IFN-gamma that are produced in response to Y. enterocolitica. Additionally, these results suggest that IL-1 alpha-induced inflammation is a major contributor to the pathology of yersiniosis.