IFNG and viral infectious disease: As cytokines play a significant role as essential mediators of the inflammatory response during a viral infection, they have also been recently tested in tears of COVID-19 patients and compared to healthy controls, indicating that out of twenty-seven cytokines that were assessed, the increase was observed in 7 of them (i.e., IL-9, IL-15, G-CSF, GM-CSF, IFN-γ, PDGF and VEGF) along with a decrease in eotaxin concentration9.