title: T cell recognition of an engineered MHC class I molecule: implications for peptide-independent alloreactivity.
abstract: Previously, we described H-2K(bW9) (K(bW9)), an engineered variant of the murine MHC class I molecule H-2K(b) (K(b)), devoid of the central anchor ("C") pocket owing to a point mutation on the floor of the peptide binding site; this substitution drastically altered selection of bound peptides, such that the peptide repertoires of K(b) and K(bW9) are largely nonoverlapping in vivo. On the basis of these observations, we used K(bW9) and K(b) to revisit the role of peptides in alloreactive T cell recognition. We first compared Ab and TCR recognition of K(bW9) and K(b). Six of six K(b)-specific mAbs, directed against different parts of the molecule, recognized K(bW9) well, albeit at different levels than K(b). Furthermore, K(bW9) readily served as a restriction element for a peptide-specific syngeneic CTL response. Therefore, K(bW9) mutation did not result in gross distortions of the TCR-interacting surface of class I, which was comparable between K(b) and K(bW9). Interestingly, when K(bW9) was used to stimulate allogeneic T cells, it induced an infrequent CTL population that cross-reacted against K(b) and was specific for peptide-independent MHC epitopes. By contrast, K(b)-induced alloreactive CTLs recognized K(b) in a peptide-specific manner, did not cross-react on K(bW9), and were present at much higher frequencies than those induced by K(bW9). Thus, induction of rare peptide-independent CTLs depended on unique structural features of K(bW9), likely due to the elevated floor of the peptide-binding groove and the consequent protruding position of the peptide. These results shed new light on the relationship between TCR and peptide-MHC complex in peptide-independent allorecognition.
authors.affiliation: Vaccine and Gene Therapy Institute and Oregon National Primate Research Center, Oregon Health and Science University, Beaverton, OR 97006, USA.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Janković
authors.forename: Kristin
authors.initials: K
authors.lastname: Remus
authors.forename: Alberto
authors.initials: A
authors.lastname: Molano
authors.forename: Janko
authors.initials: J
authors.lastname: Nikolich-Zugich
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D003429:Cross Reactions; D006183:H-2 Antigens / Q000235:genetics* / Q000276:immunology*; D066298:In Vitro Techniques; D007519:Isoantigens / Q000235:genetics; D051379:Mice; D008822:Mice, Transgenic; D010455:Peptides / Q000235:genetics / Q000276:immunology; D017354:Point Mutation; D015202:Protein Engineering; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*
chemical_list: D006183:H-2 Antigens; C032876:H-2Kb protein, mouse; D007519:Isoantigens; D010455:Peptides; D011948:Receptors, Antigen, T-Cell