IL6 and COVID-19: In this view, COVID-19-associated cytokine storm, with elevated plasma levels of IL-6, IL-1, and TNF-α, as well as ferritin and other inflammatory biomarkers, has been considered as a typical sign of sHLH/MAS, but the other “key feature” of COVID-19—the progressive lymphopenia with T cell exhaustion [4–6]—has largely been neglected.