CSF2 and pneumonia: Our findings fully supported the emerging notion that GM-CSF might be a key biomarker for SARS-CoV-2-induced cytokine storm in a subset of COVID-19 patients with more severe pneumonia often escalating to respiratory failure and death [178,179,180,181,182] (Figure 5), although the possible roles of GM-CSF and other cytokines in the pathogenesis COVID-19 remain a subject of ongoing debate [56,57].