IL18 and periodontal disorder: The effect of leptin was assessed on the expression of selected cytokines implicated in the pathogenesis of periodontal disease (IL-1, IL-6, IL-8, IL-10, IL-17, IL-18, and tumour necrosis factor-alpha [TNF-α]) at the mRNA level, as well as on the protein concentrations of these cytokines in culture supernatants.