After statistical analysis, Th17 cells and their related cytokines (IL-17, IL-6, MMP9) in the peripheral blood of AF patients were positively correlated with LAD (r = 0.493, 0.515, 0.385, 0.406, all P < 0.05), while Tim-3 + cell ratio and its related cytokines (Tim-3, Gal-9) were negatively correlated with LAD (r = − 0.484, − 0.511, − 0.381, all P < 0.05). The gene discussed is MMP9; the disease is atrial fibrillation.