Figure 1.

A, Schematic of the mild illness course for coronavirus disease 2019 (COVID-19) with an effective early innate response and an early, coordinated adaptive immune response. B, Schematic of the severe illness course for COVID-19 where an ineffective innate immune response including an attenuated type I interferon response and poor antigen presentation as well as a late uncoordinated adaptive immune response are associated with poor viral control (higher upper respiratory tract viral load) and proinflammatory, immune dysregulated profile. C-X-C motif chemokine ligand 10 (CXCL10) has been proposed as a possible biomarker for an ineffective specific T-cell response to SARS-CoV-2. Abbreviations: CXCL10, C-X-C motif chemokine ligand 10; IFN, interferon; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2; STAT, signal transducer and activator of transcription protein.