title: Major histocompatibility complex class I-specific receptors on human natural killer and T lymphocytes.
abstract: Human NK cells express several specialized inhibitory receptors that recognize major histocompatibility complex (MHC) class I molecules expressed on normal cells. The lack of expression of one or more HLA class I alleles leads to NK-mediated target cell lysis. Receptors specific for groups of HLA-C (p58), HLA-B (p70) and HLA-A (p140) alleles belong to the Ig superfamily with two or three Ig-like domains in their extracellular portion, and a long cytoplasmic tail containing ITIM motifs and associated with a non-polar transmembrane portion. In contrast, the CD94/ NKG2-A receptor complex is composed of type II proteins with a C-type lectin domain which displays a more broad specificity for different class I alleles. Recently, activatory forms of the HLA-C-specific receptors have been identified in some donors. They are virtually identical to the inhibitory forms in their extracellular portions, but display a short cytoplasmic tail lacking ITIM motifs associated with a Lys-containing transmembrane portion (p50). A subset of activated T-lymphocytes, primarily CD8+ and oligoclonal or monoclonal in nature, express NK-type class I-specific receptors. These receptors exert an inhibitory activity on T-cell receptor-mediated functions and may provide an important mechanism of down-regulation of T-cell responses.
authors.affiliation: Istituto di Istologia ed Embriologia Generale, Università di Genova, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Moretta
authors.forename: R
authors.initials: R
authors.lastname: Biassoni
authors.forename: C
authors.initials: C
authors.lastname: Bottino
authors.forename: D
authors.initials: D
authors.lastname: Pende
authors.forename: M
authors.initials: M
authors.lastname: Vitale
authors.forename: A
authors.initials: A
authors.lastname: Poggi
authors.forename: M C
authors.initials: MC
authors.lastname: Mingari
authors.forename: L
authors.initials: L
authors.lastname: Moretta
mesh_terms: D006680:HLA Antigens / Q000378:metabolism*; D006801:Humans; D007694:Killer Cells, Natural / Q000378:metabolism*; D011971:Receptors, Immunologic; D013601:T-Lymphocytes / Q000378:metabolism*
chemical_list: D006680:HLA Antigens; D011971:Receptors, Immunologic