FPG, HbA1c, FINS, CD4+ Th1 cell, CD4+ Th17 cell, interferon-gamma (IFN-γ) and interleukin-17 (IL-17) all had positive correlations with gingival index, bleeding index, probing depth and attachment loss in T2DM patients accompanied by CP (P<0.05). The gene discussed is IFNG; the disease is type 2 diabetes mellitus.