They also thank members of the Immunobiology Laboratory for advice and

discussions and Carine Joffre for her permanent support. Conflicts of Interest: The authors declare no financial or commercial conflict of interest. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. “
“Many MHC class I molecules contain unpaired cysteine residues in their cytoplasmic tail domains, the function of which remains relatively uncharacterized. Recently, it has been shown that in the small secretory vesicles known as exosomes, fully folded MHC class I dimers can Adriamycin nmr form through a disulphide bond between the cytoplasmic tail domain cysteines, MK-2206 solubility dmso induced by the low levels of glutathione in these extracellular vesicles. Here we address whether similar MHC class I dimers form in whole cells by alteration of the redox environment. Treatment of the HLA-B27-expressing Epstein–Barr virus-transformed B-cell line Jesthom, and the leukaemic T-cell line CEM transfected with HLA-B27 with the strong oxidant diamide, and the apoptosis-inducing

and glutathione-depleting agents hydrogen peroxide and thimerosal, induced MHC class I dimers. Furthermore, induction of apoptosis by cross-linking FasR/CD95 on CEM cells with monoclonal antibody CH-11 also induced MHC class I dimers. As with exosomal MHC class I dimers, the formation of these structures on cells is controlled by the cysteine at position 325 in the cytoplasmic tail domain of HLA-B27. Therefore, the redox

environment find more of cells intimately controls induction of MHC class I dimers, the formation of which may provide novel structures for recognition by the immune system. Major histocompatibility complex (MHC) class I molecules function by presenting short peptides, normally of eight or nine amino acids in length, to T cells of the immune system.1 In this manner they provide a sensitive mechanism for the detection and elimination of pathogen-infected cells. Extensive polymorphism in the residues lining the peptide-binding groove of MHC class I molecules ensures that many different pathogenic peptides can be recognized.2 MHC class I molecules are also ligands for the extensive family of killer cell immunoglobulin-like receptors (KIR) expressed on natural killer (NK) cells.3 MHC class I molecules are composed of three main domains, with the α1 and α2 domains forming the peptide-binding groove, supported underneath by the α3 domain and the non-covalently attached β2-microglobulin.4 A transmembrane-spanning domain is then followed by a cytoplasmic tail domain, the full function(s) of which remain somewhat unclear, though roles in recycling,5 targeting for degradation by ubiquitination6 and influencing recognition by NK receptors have been demonstrated.