Changes in immune cells, especially macrophages, and increases in cytokines and chemokines such as TNF-α, IL-6, IL-1β, C-X-C motif chemokine ligand 1 (CXCL1), and C-X-C motif chemokine ligand 2 (CXCL2) have also been observed in AF (45, 46). This evidence concerns the gene XCL2 and atrial fibrillation.