Moreover, T cell-mediated adaptive immune responses are crucial in the development of periodontitis, and upon activation through the T cell receptor (TCR), naive CD4+ T cells can differentiate into Th1, Th17, and Treg cells and participate in different types of immune responses (Zhu and Paul, 2010; Campbell et al., 2015; Gonzales, 2015). This evidence concerns the gene CD4 and periodontitis.