HUMAN NKR-P1A - A DISULFIDE-LINKED HOMODIMER OF THE C-TYPE LECTIN SUPERFAMILY EXPRESSED BY A SUBSET OF NK AND T-LYMPHOCYTES

In rodents, the NKR-P1 family of glycoproteins are preferentially expr essed on NK cells and have been implicated in NK cell function. In thi s study, we describe the characterization and cloning of a human homol ogue. Human (h)NKR-P1 A cDNA was cloned from a NK cell cDNA library by expression in COS7 cells with the use of the DX1 mAb. hNKR-P1 A is a type II membrane glycoprotein with characteristic properties of the C- type lectin superfamily. Comparison of the predicted amino acid of hum an NKR-P1 A with rat and mouse NKR-P1 indicates 46% homology. NKR-P1A is on human chromosome 12, the syntenic of mouse chromosome 6, where t he murine NKR-P1 genes are located. All Pat NK cells express NKR-P1; h owever, hNKR-P1A is present on only a subset of human NK cells. Althou gh rodent T cells only infrequently express NKR-P1, hNKR-P1A is presen t on similar to 25% of adult peripheral blood T cells, including both CD4(+) and CD8(+) T cells, and is expressed preferentially on adult T cells with a ''memory'' antigenic phenotype. The anti-hNKR-P1A mAb fai led to affect lysis of NK-sensitive targets; however, the spontaneous cytotoxicity mediated by certain NK cell clones against the murine P81 5 cell target was blocked by anti-hNKR-P1A mAb. Our findings demonstra te that NKR-P1A is a human homologue of the rodent NKR-P1 genes and su ggest that this molecule may be involved in NK cell function.