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BY55 is a human cell surface molecule whose expression is restricted to NK cells, a subset of circulating CD8+ T lymphocytes, and all intestinal intraepithelial T lymphocytes. Here, we report that BY55 is a novel NK receptor showing broad specificity for both classical and nonclassical MHC class I molecules, and that optimal binding requires a prior aggregation of MHC class I complexes. Using BY55 transfectants, we have identified functional consequences of MHC class I/ligand interactions for the class I-bearing cell. The triggering of MHC class I molecules on human T cell clones by BY55 delivered a potent proliferative signal in the presence of soluble CD3 mAb. The costimulatory signal provided by MHC class I ligation was only seen in activated, and not resting, peripheral blood T cells. This observation represents an additional and/or alternative pathway to CD28 costimulation and may be of particular relevance in memory T cells lacking CD28, such as intestinal intraepithelial T lymphocytes, which are CD28- but BY55+.

Type

Journal article

Journal

Journal of immunology (Baltimore, Md. : 1950)

Publication Date

02/1999

Volume

162

Pages

1223 - 1226

Addresses

Institut National de la Santé et de la Recherche Médicale U448, Henri Mondor Hospital, Faculté de Medecine, Créteil, France.

Keywords

Killer Cells, Natural, T-Lymphocytes, Cell Line, Animals, Humans, Mice, Membrane Proteins, Receptors, Immunologic, Antigens, CD28, Recombinant Proteins, Antigens, CD, Histocompatibility Antigens Class I, HLA-A2 Antigen, Ligands, Transfection, Lymphocyte Activation, Signal Transduction, Solubility, Cricetinae, GPI-Linked Proteins