Natural killer cells are non-major histocompatibility complex-restricted large granular lymphocytes that can recognize and destroy tumor cells without prior stimulation. A 150-kDa molecule on the surface of human natural killer cells was identified as a component of a putative tumorrecognition complex. We report here the isolation of cDNAs coding for the 150-kDa tumor-recognition molecule from human and mouse cDNA libraries. The amino terminus of the predicted protein contains a large hydrophobic region followed by a domain that is highly homologous to cyclophilin/peptidylprolyl ci-trans isomerase. The remainder of the protein is extremely hydrophilic and contains three homologous positively charged clusters. There are also three regions that contain extensive arginine-and serine-rich repeats. Comparison of the human and mouse predicted amino acid sequences revealed >80% homology.

Sllmmal-yIn an attempt to identify a molecule in target recognition by CD3-large granular lymphocytes (LGL), we have generated a rabbit antiidiotypic (anti-ID) serum against a monoclonal antibody (mAb 36) that reacted with the cell membrane of K562. Flow cytometry analysis demonstrated that the anti-ID serum bound selectively to CD3-LGL and that F(ab')2 fragments of the anti-ID serum blocked both target cell binding and lysis by NK cells. Stimulation of CD3-LGL with F(ab')z fragments resulted in the release of serine esterases and the secretion of interferon % Furthermore, anti-ID F(ab')2 antibodies crosslinked to anti-DNP F(ab')2 mediated directed cytotoxicity of a non-natural killer (NK)-susceptible mouse target (YAC-1) via this surface ligand. These functional reactivities were only removed by adsorption with the specific idiotype. Protein analysis showed that the anti-ID serum immunoprecipitated 80-, 110-, and 150-kD proteins. Using this anti-ID, a partial cDNA was cloned and an antipeptide antiserum was made against the portion of the predicted amino acid sequence that corresponded to a portion of the ID binding region. This antipeptide serum exhibited similar functional and biochemical reactivities to those observed with the anti-ID serum. These data suggest that the cell surface moiety recognized by the anti-ID and anti-p104 is novel and is selectively involved in both recognition and triggering of NK-mediated lytic function.

These data indicate that although all affected individuals have the cell population responsible for NK cell activity, many have cells low in expression of pNKR and lack functional NK cell activity. Overall, these results indicate that, in addition to a predisposition to the development of neoplasms, VHL patients have a defect in a specific mechanism of natural immunosurveillance that correlates with a defect in expression of a novel large granular lymphocyte pNKR protein.

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The role of a 150-kD SR-cyclophilin (NK-TR1) in monocyte differentiation was investigated. Using an antipeptide monoclonal antibody, we have detected NK-TR1 in human peripheral blood monocytes and HL-60 cells. Unstimulated monocytes showed a low intracellular level of NK-TR1 protein that increased over 3 days of lipopolysaccharide + interferon-gamma treatment, consistent with the kinetics of monocyte differentiation. Normal HL-60 cells also had a low level of NK-TR1 protein, and exposure to 1.25% dimethyl sulfoxide (DMSO) resulted in a marked transient increase in expression that returned to basal levels before the development of granulocyte differentiation-associated biochemical changes. Phorbol myristate acetate, a promoter of monocytic differentiation in HL-60 cells, also caused a significant increase in NK-TR1 over basal levels. Transfection of a vector expressing NK-TR1 antisense RNA into HL-60 cells suppressed DMSO-mediated growth arrest. In addition, the development of a more mature phenotype, as measured by expression of CD16, and the ability to reduce nitroblue tetrazoleum dye was inhibited in transfectants when compared with controls. These results are consistent with the hypothesis that the NK-TR1 gene product is required for the progression towards a mature differentiated phenotype.