Concerning systemic immunity in COVID-19, clinical studies have shown a significant rise in pro-inflammatory cytokines and chemokines (IL-1β, IL-2, IL-6, IL-8, IL-15, IFN-γ, TNF, MCP-1), characterizing cytokine release syndrome (CRS) or cytokine storm [74,75,76,77,78,79,80]. Here, IL15 is linked to COVID-19.