The genetic polymorphism in some situations may cause a change in protein that leads to a change in innate and adaptive immunity.27Some single nucleotide polymorphisms were associated with severe chronic periodontitis.11Meta-analysis study about periodontitis and IFNg +874A/T showed the inconsistency of the results of +874A/T polymorphism and periodontitis risk that may be attributed to several factors such as race, type of periodontitis, study design, and environmental factors. This evidence concerns the gene IFNG and chronic periodontitis.