SPDL1 and COVID-19: So that, the amount of sPD-L1 is increased in COVID-19 patients as compared to healthy controls [21, 22], which is correlated with a lower number of lymphocytes and partial pressure of oxygen (PaO2) to the fraction of inspired oxygen (FIO2) (P/F) as well as a higher level of C reactive protein (CRP) [22].