Identification of sensitiser modified HLA-peptides presented by keratinocytes

Skin sensitisation following the covalent modification of proteins by low molecular weight chemicals (haptenation) is mediated by cytotoxic T lymphocyte (CTL) recognition of human leukocyte antigen molecules (HLA) presented on the surface of almost all nucleated cells. There are three nonmutually exclusive models for how haptens mediate CTL recognition: direct stimulation by haptenated peptides; hapten modification of HLA leading to an altered HLA-peptide repertoire; or a hapten altered proteome leading to an an altered HLA-peptide repertoire. To address the mechanism in skin, we set out to utilise proteomic analysis of keratinocyte presented antigens following exposure to 2,4-dinitrochlorobenzene (DNCB). We show that following DNCB exposure, cultured keratinocytes present cysteine haptenated (dinitrophenylated) peptides in multiple HLA molecules. In addition, we find that one of the DNCB modified peptides derives from the active site of cytosolic glutathione-S transferase-ω. These results provide support for the hypothesis that a key mechanism of skin sensitisation is stimulation of CTLs by haptenated peptides.