[The roles of heat shock proteins in host defense against bacterial infection]

Heat shock proteins (HSP) are widely distributed in nature, and are highly conserved proteins among prokaryotes and eukaryotes. These proteins are known to be involved in cytoprotection against various stress conditions including bacterial infection, and immune responses to various pathogens such as bacteria. In this study, we showed that HSP70 protected macrophages infected with Salmonella choleraesuis against TNF-alpha-induced cell death. Furthermore, HSP70-reactive CD4+ T cells appeared during the course of infection with Listeria monocytogenes. These cells produce TGF-beta and IL-10 in response to HSP70, which in turn regulate Th1-cell-mediated excessive inflammation after the battle against bacteria has been won. Thus, HSPs play important roles in protecting against excessive inflammation not only via cytoprotection but also induction of immunoregulatory T cells.