Quantitative analysis of HLA-B27 by flow cytometry using CD3 gating in seronegative spondylarthropathies

Objective To investigate the relationship in patients with spondylarthropathies (SpA) between the clinical features of the disease and quantitative flow cytomet ric expression of HLA-B27 by CD3 gating. Methods We performed quantitative analysis of HLA-B27 antigen by flow cytometry usi ng CD3 gating in 61 patients with seronegative and HLA-B27 positive SpA. Th e patients included 29 with ankylosing spondy-litis (AS), 29 with undiffere ntiated spondylarthropathy (uSpA), and 3 with reactive arthritis (ReA). In addition, we compared the fluorescence intensity of HLA-B27 with the clinic al characteristics of the patients. Results The fluorescence intensity of HLA-B27 was significantly higher in patients with AS than in patients with other SpAs (220.5 +/- 13.7% vs 182.8 +/- 11.7 %, p = 0.04). However, there were no demonstrable correlations between the quantitative expression of B27 and clinical features such as age, disease d uration, results of the Schober test, chest expansion, the WBC count, eryth rocyte sedimentation rate (ESR) and C-reactive protein (CRP). There was als o no difference in the quantitative expression of HLA-B27 based on the pres ence or absence of uveitis, peripheral arthritis or enthesopathy. However; multiple regression analysis showed that age, disease duration and CRP were independent factors influencing the quantitative expression of HLA-B27 in SpA (beta = 0.568, 0.546, -0.437 and p = 0.006, 0.02, 0.04, respectively). Conclusions Our data suggest that the quantitative expression of HLA-B27 may be related to some of the clinical features inpatients with SpA.