Abstract
BackgroundThe natural cytotoxicity receptors (NCR) are important to stimulate the activity of Natural Killer (NK) cells against transformed cells. Identification of NCR ligands and their level of expression on normal and neoplastic cells has important implications for the rational design of immunotherapy strategies for cancer.Methodology/Principal FindingsHere we analyze the expression of NKp30 ligand and NKp44 ligand on 30 transformed or non-transformed cell lines of different origin. We find intracellular and surface expression of these two ligands on almost all cell lines tested. Expression of NKp30 and NKp44 ligands was variable and did not correlate with the origin of the cell line. Expression of NKp30 and NKp44 ligand correlated with NKp30 and NKp44-mediated NK cell lysis of tumor cells, respectively. The surface expression of NKp30 ligand and NKp44 ligand was sensitive to trypsin treatment and was reduced in cells arrested in G2/M phase.Conclusion/SignificanceThese data demonstrate the ubiquitous expression of the ligands for NKp30 and NKp44 and give an important insight into the regulation of these ligands.
Highlights
Natural Killer (NK) cells represent a unique subset of lymphocytes that can mediate innate immune responses against tumors and certain pathogens [1,2,3]
We demonstrate that NKp30 ligand (NKp30L) and NKp44 ligand (NKp44L) are ubiquitously and variably expressed on transformed and non-transformed cell lines
When we extended our analysis to more tumor cell lines of different origin we detected NKp30L and NKp44L on the surface of almost all cell lines tested (Fig. 4A)
Summary
Natural Killer (NK) cells represent a unique subset of lymphocytes that can mediate innate immune responses against tumors and certain pathogens [1,2,3]. Recent studies with patients receiving hematopoietic stem cell transplantation demonstrated an important role of NK cells for eradicating certain types of hematopoietic tumors [7]. This potent anti-tumor activity of NK cells is regulated by the engagement of NK cell surface receptors, cytokines and the crosstalk with other immune cells [8,9,10]. Non-MHC class I recognizing inhibitory receptors seem to be important for regulating NK cell activity [12]. These data demonstrate the ubiquitous expression of the ligands for NKp30 and NKp44 and give an important insight into the regulation of these ligands
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