Abstract: Objective　To investigate the change and significance of CD3⁺CD(16, 56)⁺ natural killer(NK) T cells in peripheral blood of patients with rheumatoid arthritis(RA). Methods　The percentage 　of CD3⁺CD(16, 56)⁺ T cells and the expression of activation marker CD69 on CD3⁺CD(16,56)⁺ T cells in peripheral blood lymphocyte from active and inactive RA patients and healthy subjects as controls were determined by flow cytometry. Results　Compared with healthy controls and inactive RA patients, the active RA patients had a lower percentage of CD3⁺CD(16,56)⁺ NK T cells and downregulated expression of CD69 on CD3⁺CD(16, 56)⁺ NK T cells (P<0.01). The percentage of NK T cells and CD69 expression on CD3⁺CD(16,56)⁺ T cells　had no statistical significance between healthy controls and inactive RA patients (P>0.05). Conclusions　Low percentage of CD3⁺CD(16,56)⁺ NK T cells with downregulated expression of CD69 in peripheral blood may play a potential role in the pathogenesy of RA and be relevant to the activity of RA.

Key words: Natural killer T cell, Rheumatoid arthritis, Flow cytometry