IL2 and atrial fibrillation: The peripheral blood of patients with RA contains citrulline-specific T cells, of which ~40% of the samples are positive for the Th1 marker chemokine receptor 3 (CXCR3) (21), and plasma concentrations of IL-2 and IFN-γ, which are also biomarkers of Th1 cells, are significantly elevated in patients with AF (13, 22, 23).