JAG1 and periodontitis: Considering the critical role of the JAG1–NOTCH2 axis in macrophage-mediated inflammation and our prior findings of a significant upregulation of the JAG1–NOTCH2 ligand–receptor pairs in both human and mouse gingival epithelial cells and macrophages during periodontitis, we investigated the specific role of this axis in epithelial–macrophage interactions.