Crossrecognition by CD8 T cell receptor αβ cytotoxic T lymphocytes of peptides in the self and the mycobacterial hsp60 which share intermediate sequence homology

Abstract

Immunization of C57BL/6 mice with the mycobacterial heat shock protein (hsp) 60 in immunostimulating complexes caused the in vivo activation of autoreactive major histocompatibility complex class I (H‐2D^b)‐restricted CD8 T cell receptor (TcR) α/β cells. A CD8 TcR α/β 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‐γ (IFN‐γ) stimulation. The stress‐induced, self peptide could be extracted from IFN‐γ‐stressed macrophages by acid elution, suggesting that the IFN‐γ‐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‐γ‐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.