CROSSRECOGNITION BY CD8 T-CELL RECEPTOR-ALPHA-BETA CYTOTOXIC T-LYMPHOCYTES OF PEPTIDES IN THE SELF AND THE MYCOBACTERIAL HSP60 WHICH SHARE INTERMEDIATE SEQUENCE HOMOLOGY

Immunization of C57BL/6 mice with the mycobacterial heat shock protein (hsp) 60 in immunostimulating complexes caused the in vivo activation of autoreactive histocompatibility complex class I (H-2D(b))-restricted CD8 T cell receptor (TcR) alpha/beta cells. A CD8 TcR alpha/beta clone with specificity for the mycobacterial hsp60 peptide(499-508) was derived from this immunization,which, in addition, recognized syngeneic macrophages which had been stressed by interferon-gamma (IFN-gamma) stimulation. The stress-induced, self peptide could be extracted from IFN-gamma-stressed macrophages by acid elution, suggesting that the IFN-gamma-induced self peptide is derived from an endogenous protein. Based on our observation that lysis of stressed target cells by this cytotoxic T lymphocyte (CTL) clone was specifically inhibited by hsp60-specific antisense oligonucleotides, we used synthetic peptides representing amino acid (aa) sequences of the murine hsp60 for target cell sensitization and identification of the relevant self peptide. Synthetic peptides representing 9-mer to 11-mer aa sequences of the murine hsp60 with asparagine in anchor position 4 or 5 as the minimal requirement for H-2D(b) binding were tested in CTL assays. The overlapping murine hsp60 peptides(162-170/171) were stimulatory at a concentration as low as 10-100 pM. Seven other peptides of the murine hsp60 required intermediate peptide concentrations of 10-100 nM for recognition by the CTL clone. Although the murine and mycobacterial hsp60 peptides recognized by this CTL clone showed only intermediate homology (3 identical and 3 similar aa), our data suggest that endogenous hsp60 itself is the source of self peptide(s) presented by IFN-gamma-stressed macrophages to the cross-reactive CTL clone with promiscuous specificity. This notion is consistent with the idea of hsp as a link between infection and autoimmunity.