Despite the presence of chronic periodontitis not appearing to influence the systemic expression of the genes studied, this study showed a correlation between lower expression of IFNG and IP10 and higher expression of IL10 and IFNA with the severity of chronic periodontitis (higher percentage of visible plaque, marginal bleeding, BP, PPD ≥ 6 mm, CAL ≥ 5 mm, and suppuration). The gene discussed is IFNG; the disease is periodontitis.