Objective: To explore the effects of NKp44+NK cells from rheumatoid arthritis (RA) patients on the proliferation and monocyte chemotactic protein 1 production of fibroblast-like synoviocytes (FLS).
Methods: The proportions of natural killer (NK) p44 NK cells in peripheral blood (PB) of 50 RA patients and 50 healthy individuals were detected by flow cytometry. Synovial fluid (SF) samples from 30 RA patients were also detected. NKp44+NK cells in RA SF were sorted by flow cytometry for 5 times. The supernatant level of interleukin (IL)-22 was measured by enzyme-linked immunosorbent assay (ELISA). The proliferation of FLS after an addition of culture supernatant of NKp44+NK cells was detected by methyl thiazolyl tetrazolium (MTT) at 24, 48 and 72 h. Monocyte chemotactic protein (MCP)-1 production of RA FLS after an addition of rhIL-22 was detected by ELISA.
Results: The proportion of NKp44+NK cells in PB of RA patients was significantly higher than that of normal controls while the proportion of NKp44+NK cells in SF of RA patients was higher than that in PB of matched RA patients (1.270% vs 0, 15.190% vs 2.425%, P < 0.01). The supernatant level of IL-22 in NKp44+NK cell culture was (1 603 ± 332) ng/L. Rapid proliferation of RA FLS was observed at 24, 48, 72 h after an addition of culture supernatant (P < 0.01). IL-22 antibody obviously inhibited the proliferation of RA FLS induced by NKp44+NK cells. MCP-1 production of RA FLS was detected at 72 h after an addition of rhIL-22 (P < 0.01).
Conclusion: NKp44+NK cells can promote the proliferation and MCP-1 production of RA FLS through the production of IL-22 so as to play an important role in the synovial proliferation and inflammation of RA.