CCL2 and periodontitis: For instance, attracted by chemokine (C–C motif) ligand 2 (CCL2) and other chemokines being highly expressed in gingival fibroblasts (Williams et al. 2021), macrophages infiltrate the connective tissue and contribute to innate immunity, particularly during periodontitis and peri-implantitis (Williams et al. 2021; Carcuac and Berglundh 2014).