S100A8 and COVID-19: Given that a positive feedforward loop between S100A8/9 and IL-6 can drive pro-inflammatory circuit50–52 and that elevated serum S100A8/9 is one of the hallmarks of severe COVID-19 patients53,54, it is possible that tocilizumab can exert its effect partly through the inhibition of S100A8/9 expression in COVID-19.