COVID-19(15) Coronavirus disease 2019(10) airway(9) Methylprednisolone therapy(6) Methylprednisolone(6) Serum level(6) Respiratory failure(6) mast cell(6) pulse(6) serum(6) conducted(6) histological(6) endoscopy(6) Mast cells(6) Clinical severity(6) Corticosteroid(6) hypersensitivity reactions(6) Corticosteroids(6) cell activation(6) pulmonary(6) severe COVID-19.(6) detect(6) correlated(6) Severity Score(6) AhR(6) pulse methylprednisolone therapy(6) hypersensitivity(6) coronavirus disease(6) S1 protein(6) severe COVID-19(6)