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 cytometric expression of HLA-B27 by CD3 gating. Methods: We performed quantitative analysis of HLA-B27 antigen by flow cytometry using CD3 gating in 61 patients with seronegative and HLA-B27 positive SpA. The patients included 29 with ankylosing spondylitis (AS), 29 with undifferentiated spondylarthropathy (uSpA), and 3 with reactive arthritis (ReA). In addition, we compared the fluorescence intensity of HLA-B27 with the clinical 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 duration, results of the Schober test, chest expansion, the WBC count, erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP). There was also no difference in the quantitative expression of HLA-B27 based on the presence 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 (β = 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 in patients with SpA.