Major histocompatibility complex class I-specific receptors on human natural killer and T lymphocytes.
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.
Moretta
A
A
Istituto di Istologia ed Embriologia Generale, Università di Genova, Italy.
Biassoni
R
R
Bottino
C
C
Pende
D
D
Vitale
M
M
Poggi
A
A
Mingari
M C
MC
Moretta
L
L
D006680:HLA Antigens / Q000378:metabolism*; D006801:Humans; D007694:Killer Cells, Natural / Q000378:metabolism*; D011971:Receptors, Immunologic; D013601:T-Lymphocytes / Q000378:metabolism*
D006680:HLA Antigens; D011971:Receptors, Immunologic