Increased proportion and abnormal phenotype of NK cells in peripheral blood of patients with knee osteoarthritis

Objective To investigate the distribution and phenotypic characteristics of natural killer (NK) cells in the peripheral blood of knee osteoarthritis (KOA) patients. Methods Flow cytometry was used to detect and compare the distribution of NK cells and the expression of their surface functional receptors in the peripheral blood of healthy controls without KOA and patients with KOA, such as human leukocyte antigen DR (HLA-DR) and natural cytotoxicity receptor 3 (NCR3/NKP30). Results The proportion of NK cells in the peripheral blood of KOA patients was significantly up-regulated, especially CD16bright NK cells. The expression of HLA-DR molecules on the surface of NK cells with KOA was up-regulated, while the expression of NKP30 was significantly down-regulated. Conclusion The proportion of NK cells in the peripheral blood of KOA patients increases, and the cells show the up-regulated expression of CD16 and HLA-DR and the down-regulated expression of NKP30.