For example, in critically ill patients of COVID-19 the expression of inflammatory cytokines including IL-2, IL-6, IL-7, IL-10, IP-10, MCP-1, TNF-α, and IFN-γ has been shown to be excessively elevated, and this kind of cytokine storm is thought as the main cause of multi-organ failure and death in COVID-19 patients (Castelli et al., 2020; Hu et al., 2021; Luo et al., 2022). Here, IL2 is linked to COVID-19.