IL17A and periapical granuloma: On estimation of IL-21 levels in periapical granulomas, it was demonstrated that IL-21 along with IL-17A, TNF-α (tumour necrosis factor-α), and IFN-γ were higher in active periapical granulomas, while IL-4, IL-9, IL-10, and IL-22 were higher in inactive periapical granulomas.