IFNG and COVID-19: Given the down‐regulation of CD28 signalling, immediate up‐regulation of gene‐related PGE2 synthases (i.e., PTGS1, PTGS2, and PTGES3) at the early stages post‐SARS‐CoV‐2 infection, and the kinetics of PGE2 secretion in COVID‐19 patients (Hong et al., 2020; Yan et al., 2020; Z. Zhou, Ren, et al., 2020), it is proposed that PGE2 may inhibit the development of inflammatory IFN‐γ‐producing Th1 cells, although further investigations are required.