Macrophages as main inducers of IFN-g in T cells following administration of human and mouse heat shock protein 60 Minka Breloer 1 , Solveig H. More  1 , Anke Osterloh 1 , Felix Stelter 2 , Robert S. Jack 2 and Arne von Bonin 1 1 Bernhard-Nocht-Institute for Tropical Medicine, Bernhard-Nocht Strasse 74, 20359 Hamburg, Germany 2 Institute of Immunology and Transfusion Medicine, Ernst-Moritz-Arndt-University, 17489 Greifswald, Germany Keywords: antigen-presenting cell, danger signal, dendritic cell, Hsp60 Abstract Human Hsp60 (hHsp60) elicits a potent pro-in¯ammatory 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 speci®c secretion of high amounts of IFN-g in T cells with PEC as antigen-presenting cells (APC). Although DC are highly ef®cient APC, they were much less potent as inducers of IFN-g in the presence of Hsp60. The IFN-g-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-g in TCR transgenic T cells. These results demonstrate that mHsp60 as an endogenous `self' molecule can induce an in¯ammatory 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 ®nely tuned activation of cells from the innate and adaptive immune system by `self' Hsp60 that depends strongly on the type of APC. Introduction Heat shock proteins (HSP) are thought to protect against cellular stress (1). From an immunological point of view it has been shown that eukaryotic HSP, besides their peptide- speci®c effects (2±6), e.g. in generating a cytotoxic T lymphocyte response (7), serve as danger signals (8) to the innate immune system (9±11). Murine and human macro- phages were found to elicit a profound pro-in¯ammatory response when incubated with recombinant human Hsp60 (hHsp60) (12). The response included the up-regulation of co- stimulatory molecules, and the release of in¯ammatory cytokines like IL-6 and tumor necrosis factor (TNF)-a. It was shown that CD14, a monocyte receptor for lipopolysaccharide (LPS), is necessary for hHsp60-mediated signaling (13). CD14 is a GPI-linked receptor which has no transmembrane domain. Signaling through CD14 requires the Toll-like receptor (TLR)-4 molecule as a co-receptor. Activation of monocytes and macrophages by hHsp60 depends on the presence of TLR-4 and mice carrying a mutant TLR-4 are non-responsive to Hsp60 (14). We have recently shown that hHsp60, in addition to its ability to activate professional antigen-presenting cells (APC), also in¯uences the activation of T cells. Addition of hHsp60 to cultures containing peritoneal exudate cells (PEC) and ex vivo puri®ed T cells, expressing transgenic MHC class I- or -II- restricted TCR speci®c for chicken ovalbumin (OVA)-derived peptides, speci®cally induce a release of IFN-g (15). In contrast, proliferation and IL-2 secretion were not changed in cultures containing hHsp60. So far, we have no information as to whether dendritic cells (DC) (16), the most potent APC, are able to respond to Hsp60 by inducing increased IFN-g release from T cells. In addition, little is known as to whether Hsp60 molecules derived from different species in¯uence the activation of the innate immune system. The high degree of sequence identity of mammalian Correspondence to: A. von Bonin; E-mail: Arne_von_Bonin@magicvillage.de Transmitting editor: S. H. E. Kaufman Received 16 March 2002, accepted 19 July 2002 International Immunology, Vol. 14, No. 11, pp. 1247±1253 ã 2002 The Japanese Society for Immunology by guest on August 6, 2015 http://intimm.oxfordjournals.org/ Downloaded from