Macrophages as main inducers of IFN-γ in T cells following administration of human and mouse heat shock protein 60

Human Hsp60 (hHsp60) elicits a potent pro-inflammatory response in cells of the innate immune system. Here we compared the capacity of peritoneal exudate cells (PEC) and bone marrow-derived dendritic cells (DC) to stimulate murine T cells in the presence of Hsp60. Hsp60 induced a specific secretion of high amounts of IFN-gamma in T cells with PEC as antigen-presenting cells (APC). Although DC are highly efficient APC, they were much less potent as inducers of IFN-gamma in the presence of Hsp60. The IFN-gamma-inducing effect of Hsp60 is dependent on co-stimulatory signals provided by B7-CD28 interactions. In addition to hHsp60, we used syngenic murine recombinant Hsp60 (mHsp60) and show that mHsp60 also induces IFN-gamma in TCR transgenic T cells. These results demonstrate that mHsp60 as an endogenous 'self' molecule can induce an inflammatory response. Interestingly, mHsp60, although sharing >98% protein sequence identity with the hHsp60 homologue, does not bind to human CD14 molecules. Taken together, our results indicate a finely tuned activation of cells from the innate and adaptive immune system by 'self' Hsp60 that depends strongly on the type of APC.