In patients with chronic periodontitis and periodontitis associated with genetic immune deficiencies, such as leukocyte adhesion deficiency type 1 (LAD1), IL-23 was highly expressed by epithelial cells in close proximity to periodontal tissues suggesting that epithelial-derived IL-23 controls disease activity (Figure 1) (129). The gene discussed is IL23A; the disease is leukocyte adhesion deficiency 1.