IL6 and immunodeficiency disease: According to a review study, elderly age, male gender, preexisting hypertension, diabetes, obesity, COPD, tumor, immunodeficiencies, pregnancy, thromboembolism, coagulation disorders, leukocytosis, lymphopenia, eosinopenia, elevated serum levels of D-dimer, LDH, AST and ALT, BUN and creatine, cTnI, CRP, PCT, IL-6, IL-1β, KL-6, ferritin, higher CT pneumonia score, high number of affected pulmonary lobes, and smoking are major risk factors of severe clinical course and outcomes in patients with COVID-19 [31].