Objective       To investigate the frequency of CD161

+

T cells in peripheral blood mononuclear cells (PBMCs) from patients with rheumatoid arthritis (RA).       Methods       A total of 21 patients diagnosed as RA (14 women and 7 men

at an average age of 55) who hospitalized in our department from June 2009 to June 2010 were enrolled in this study. Another 21 age- and

sex-matched healthy volunteers served as normal control. PBMCs were obtained from RA patients and healthy subjects. CD161 positive T cells were identified by a four-color flow cytometer after ex vivo stimulation with phorbol myristate acetate and ionomycin in the present of brefeldin A (BFA).       Results       The frequencies of CD161

+

T cells and CD161

+

Th1 cells were significantly decreased within CD4

+

T cells of PBMCs from RA patients

respectively [(27.53±7.34)% vs (22.75±5.11)%

P0.05; (11.35±4.36)% vs (8.21±3.93)%

P0.05

]

which led to a decreased percentage of CD161

+

and CD161

-

Th1 cells in RA patients.       Conclusion       The inflammatory response of synovial membrane in RA patients results in the changes of CD161

+

CD4

+

T cells and CD161

+

Th1 cells

rather than those of the corresponding CD161

-

T cells

which suggests CD161

+

T cells might play an important role in the development of RA.