OBJECTIVETo investigate the expression of CD160 on the surface of human natural killer (NK) cells and its possible relationship with hematological malignancies.

METHODSCD160 expression on human leukemia cell line NK92 cells was confirmed by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot. The proliferation characteristics and cell surface markers of this cell line were determined. Cytotoxicity of NK92 against 2 human myeloid leukemia cell lines, K562 and THP-1 was analyzed ex vivo. CD160 blocking antibody CL1-R2 was employed to clarify its role in NK cell mediated cytolysis. Then, the expression of CD160 on NK cells in peripheral blood from various patients with hematological malignancies were measured by flow cytometry.

RESULTSThe mRNA and protein levels of CD160 expressions on NK92 cells were confirmed by RT-PCR and Western blot, respectively. The flow cytometry results demonstrated that the strong positive expression of CD160 could be detected on the NK92 cell surface. NK92 could effectively kill K562 and THP-1 cells, while the cytolysis effect was abrogated in the presence of CD160 blocking antibody CL1-R2. The high levels of HVEM were expressed on both target cells, but the HLA class I molecules were absent on K562. The expression of CD160 on CD3CD56 NK cells in peripheral blood from patients with acute myeloid leukemia (AML), chronic lymphocytic leukemia (CLL) and allogeneic hematopoietic stem cell transplantation (allo-HSCT) recipients was significant lower than that in the normal controls (P<0.05).

CONCLUSIONThe cytolysis function of human NK cells is mediated partially by CD160 molecule. The decrease of CD160 expression on NK cells from patients with various hematological malignancies implies that down-regulation of CD160 expression may be a novel mechanism of tumor immune escape.