IL18 and atherosclerosis: Several studies reported the role of IFN-γ and IL-18 in the pathogenesis of atherosclerosis [56,57,58], and our findings related to the association of GCF concentrations of IFN-γ, IL-12, and IL-18 with IMT support the proposed concept that an increased Th1 response caused by PD could be a risk factor for atherosclerosis even in its early stage.