Sepsis, including viral infections, are major causes of death worldwide. Studies show that in
2017, the number of sepsis patients worldwide reached as high as 48.9 million, of which 11
million patients died. Studies in China also showed that more than 1 million patients died of
sepsis in 2015. Previous studies have suggested that sepsis are often secondary to excessive
inflammatory response syndrome. However, treatment measures targeting excessive inflammatory
response failed to effectively improve the prognosis of patients. PD-1 and PD-L1 are key
mediators in T cell depletion in sepsis patients. Therefore, the investigators try to
performe a clinical research to investigate the efficacy of PD-1 and thymosin in patients
with severe pneumonia associated with lymphocytopenia in 2019 novel coronavirus infection.