Elevated expression of TIGIT on CD3+CD4+ T cells correlates with disease activity in systemic lupus erythematosus

OBJECTIVES It is well-known that lymphocytes play an important role in systemic lupus erythematosus (SLE). T cell immunoreceptor with Ig and immunoreceptor tyrosine-based inhibitory domains (TIGIT) is one of immunosuppressive costimulatory molecules that mediates an inhibitory effect. However, its roles in SLE are poorly understood. This study was designed to investigate the correlation between the frequencies of TIGIT-expressing CD3+CD4+ T lymphocytes and SLE. METHODS Patients with SLE were recruited from the First Affiliated Hospital of Nanchang University. Medical history, clinical manifestations, physical examination and laboratory measurements were recorded. The expression of TIGIT on CD3+ T lymphocytes, B lymphocytes, monocytes, neutrophils, CD3+CD4+ T lymphocytes and CD3+CD8+ T lymphocytes were determined by flow cytometry. The frequencies of TIGIT-expressing CD3+CD4+ T lymphocytes in patients with SLE were further analyzed for correlations with markers of autoimmune response, inflammation, urine proteins and disease activity in SLE. RESULTS The frequency of TIGIT-expressing CD3+CD4+ T lymphocytes was significantly elevated in SLE patients compared with healthy controls (P < 0.0001). The frequency of TIGIT-expressing CD3+CD4+ T lymphocytes in patients with SLE was increased significantly in subjects with high anti-dsDNA titer (P = 0.026), high anti-Sm titer (P = 0.026), and high levels of urine microalbumin (P = 0.046). Furthermore, The frequency of TIGIT-expressing CD3+CD4+ T lymphocytes was found to be positively correlated with the Disease Activity Index (SLEDAI) score in SLE (r2 = 0.082; P = 0.044). CONCLUSION In SLE, the frequency of TIGIT-expressing CD3+CD4+ T lymphocytes was elevated and associated with the disease activity.