Insulin B:9-23 peptide-reactive γδ T cells in the non-obese diabetic (NOD) mouse recognize an oxidized dimeric form of the peptide (123.23)

Abstract

Abstract The insulin peptide ins2 B:9-23 is recognized by diabetogenic αβ T cells in NOD mice, and by γδ T cells. Unlike the αβ T cell response to the peptide, the γδ T cell response is independent of APCs. Furthermore, the cysteine residue in position 19 of the peptide is required for the γδ but not the αβ response. Since cysteine residues can dimerize upon oxidation, we hypothesized that γδ T cells recognize oxidized dimeric peptide molecules. We therefore compared the stimulatory activities of monomeric, copper chloride-oxidized (mostly dimeric) and DMSO-oxidized, HPLC-purified dimeric insulin peptide B:9-23 preparations. We found that oxidized and purified dimeric peptide preparations stimulated γδ T cells far better than untreated or purified monomeric preparations, which still contained some oxidized peptides. In contrast, αβ T cells responded only to monomeric peptides except when live APCs were present. The γδ T cell response to the dimeric insulin peptide was TCR dependent because responsiveness could be transferred with transduced TCR-γ/δ genes derived from the originally described B:9-23-reactive γδ T cell hybridoma SP9D11. These findings provide an explanation for the differential response requirements of insulin peptide-reactive αβ and γδ T cells, and they raise the possibility that B:9-23-reactive γδ T cells function as sensors of oxidative stress.