Abstract:

Objective: To detect the levels of Dickkopf-1 (DKK-1) in the plasma of patients with rheumatoid arthritis (RA), and to analyze their correlation with peripheral blood T cell subsets and clinical indicators. Methods: Enzyme-linked immunosorbent assay (ELISA) was used to detect plasma DKK-1 levels in 32 RA patients and 20 healthy controls, and to record the various clinical manifestations and laboratory indicators of the RA patients, and flow cytometry to detect peripheral blood T cell subsets in the RA patients (Including Treg, nTreg, aTreg, sTreg, Teff, Tfh, CD4⁺CD161⁺T, CD8⁺T, CD8⁺CD161⁺T cells). The plasma DKK-1 levels between the two groups were ompared, and its correlation with peripheral blood T cell subsets and clinical indicators analyzed. Results: (1) The plasma DKK-1 concentration of the RA patients was (124.97±64.98) ng/L. The plasma DKK-1 concentration of the healthy control group was (84.95±13.74) ng/L. The plasma DKK-1 level of the RA patients was significantly higher than that of the healthy control group (P<0.05), and the percentage of CD8⁺CD161⁺T cells in the peripheral blood of the RA patients was significantly higher than that of the healthy control group (P<0.05). (2) The plasma DKK-1 level was positively correlated with erythrocyte sedimentation rate (r=0.406, P=0.021),DAS28 score (r=0.372, P=0.036), immunoglobulin G(r=0.362, P=0.042), immunoglobulin A(r=0.377, P=0.033) ; it had no correlation with age, course of disease, C-reactive protein, rheumatoid factor, anti-cyclic citrullinated peptide antibody, immunoglobulin M, complement C3, complement C4, white blood cell, neutrophil ratio. (3) The plasma DKK-1 level in the RA patients was positively correlated with the percentage of peripheral blood CD161⁺CD8⁺T cells (r=0.413, P=0.019);it had no correlation with Treg, nTreg, aTreg, sTreg, Teff, Tfh, CD4⁺CD161⁺T, CD8⁺T cells. (4) The percentage of CD161⁺CD8⁺T cells was negatively correlated with erythrocyte sedimentation rate (r=-0.415, P=0.004), C-reactive protein (r=-0.393, P=0.007), DAS28 score(r=-0.392, P=0.007),rheumatoid factor (r=-0.535, P<0.001), anti-citrullinated protein antibody (r=-0.589, P<0.001), immunoglobulin G(r=-0.368, P=0.012) immunoglobulin M (r=-0.311, P=0.035); it had no correlation with age, disease course, immunoglobulin A, complement C3, complement C4,white blood cell,and neutrophil ratio. Conclusion: RA patients’ plasma DKK-1 levels and the percentage of CD8⁺CD161⁺T cells in T cell subsets in peripheral blood increase, which may be related to the secretion of proinflammatory cytokines in patients; DKK-1 is involved in the regulation of bone homeostasis and can be used as a marker of bone destruction in RA.

Key words: Rheumatoid arthritis, Dickkopf-1, T cells