In vivo and in vitro activation of T cells after administration of Ag-negative neat shock proteins

Heat shock proteins (HSP) Hsp70 and gp96 prime class I-restricted cytotoxic T cells against Ags present in the cells from which they were isolated, Th e immunization capacity of HSPs is believed to rely on their ability to bin d antigenic peptides, In this study, we employed the well-established OVA a nd beta-galactosidase (beta-gal) antigenic model systems. We show that in v itro long-term established OVA and beta-gal-sperific CTL clones release TNF -alpha and IFN-gamma when incubated with Ag-negative Hsp70 and gp96, In the absence of antigenic peptides, HSP-mediated secretion of TNF-alpha and IFN -gamma requires cell contact of the APC with the T cell but is not MHC-I re stricted, Moreover, Hsp70 molecules purified from Ag-negative tissue, e.g., negative for antigenic peptide, are able to activate T cells in vivo, lead ing to significant higher frequencies in OVA-specific CD8(+) T cells. In un primed animals, these T cells lyse OVA-transfected cell lines and produce T NF-alpha and IFN-gamma after Ag stimulus. Taken together our data show that , besides the well-established HSP/peptide-specific CTL induction and activ ation, a second mechanism exists by which Hsp70 and gp96 molecules activate T cells in vivo and in vitro.