It is synthesized in response to infections or trauma [129], mainly by macrophages, neutrophils, keratinocytes, gingival fibroblasts and endothelial cells [132,133], meaning that under normal conditions, IL-6 levels are very low; however, these can increase in inflammatory states [130], as seen in patients with periodontitis and other systemic diseases [134,135]. Here, IL6 is linked to periodontitis.