IFNG and periodontitis: Studies have suggested that specific cytokines (elastase, interleukin -IL-1, IL-2, IL-6, IL-13, IFN-γ, TNF-α) were increased while others are decreased (IL-1β, IL-18) in either GCF or serum of SLE subjects (20–22), and similar alterations were observed in periodontitis patients (23).