S100A8 and COVID-19: Incubation of these cells with S100A8/A9 dimer, a potent proinflammatory signaling molecule that is abundant in inflamed tissues from patients with COVID-19,8,36,37 upregulated the expression of IFN (interferon)-α, IL-1β, IL-6, IL-10, and TNF-α (Figure 7B through 7F).