TNF-a is strongly correlated to the incidence and exacerbation of periodontitis in diabetes mellitus.30TNF-a is a major cytokine released by activated macrophages, monocytes, and T lymphocytes which affect growth regulation, immune response, survival, differentiation, and physiological functions of different cells together with the production of other enzymes, mediators, and cytokines. The gene discussed is TNF; the disease is diabetes mellitus.