Conclusion:
The clinical, immunological, and pathologic features of COVID-19 have something in common with SARS and MERS. All the viruses can cause lymphopenia and influenza-like symptoms in the early stage. SARS and COVID-19 do not lead to the elevation of TNF-α, but the increase of IL-6 and IL-10 is more common in COVID-19. The IL-6 plays a crucial role in the pathologic of COVID-19, including the chemotaxis of neutrophils and lymphocyte necrosis. Importantly, COVID-19 is more able to cause cytotoxic lymphocytes exhaustion.