Table 1. Main Acute-Phase Proteins and Their Role in Covid-19.*.
| Function and Protein or Proteins | Degree and Type of Change in Inflammatory Conditions† | Role or Roles in Covid-19 and Associated Conditions‡ |
|---|---|---|
| Humoral innate immunity | ||
| C-reactive protein | ↑↑↑↑ | Association with death, ICU admission, need for interleukin-6 inhibition, and PASC11-14 |
| Serum amyloid P | ↑ or → | ND |
| Serum amyloid A | ↑↑↑↑ | Association with severity15 |
| PTX3 | ↑↑↑ | Association with death, lung lesions on CT, response to interleukin-6 inhibition, intubation, thrombotic events, and PASC16-19 |
| C1q, C3, and C4 | ↑ | Association with pathogenesis20,21 |
| C4-binding protein | ↑ | ND |
| Mannose-binding lectin | ↑↑ or → | Viral inhibition, association with thromboembolism22 |
| Interleukin-1Ra | ↑↑ | Association between anti–interleukin-1Ra autoantibodies and severity, MIS-C, or myocarditis after SARS-CoV-2 vaccination23 |
| Coagulation or tissue repair and remodeling | ||
| Fibrinogen | ↑↑ | Association of d-dimer with thromboembolism14 |
| Prothrombin | → | ND |
| Fibronectin | ↑ or → | ND |
| α2-Macroglobulin | ↑ | ND |
| Antithrombin III | ↓ | ND |
| α1-Antitrypsin | ↑↑ | ND |
| α1-Antichymotrypsin | ↑↑ | ND |
| Urokinase-type plasminogen activator | ↑ | ND |
| Thrombopoietin | ↑↑ | ND |
| Iron metabolism | ||
| Transferrin | ↓ | ND |
| Ferritin | ↑↑ | Association with ICU admission and mechanical ventilation14,24 |
| Haptoglobin | ↑↑ | ND |
| Hemopexin | ↑ | ND |
| Hepcidin | ↑↑ | ND |
| Other carrier proteins | ||
| Albumin | ↓ | ND |
| Ceruloplasmin | ↑ or → | ND |
| Apolipoproteins | ↓ | ND |
| α1-Acid glycoprotein | ↑↑ | ND |
*
Covid-19 denotes coronavirus disease 2019, CT computed tomography, ICU intensive care unit, MIS-C multisystem inflammatory syndrome in children, ND not determined, PASC postacute sequelae of Covid-19, PTX3 pentraxin 3, and SARS-CoV-2 severe acute respiratory syndrome coronavirus 2.
†
Upward-pointing arrows (↑) and downward-pointing arrows (↓) indicate increases and decreases in concentration, respectively; a right-pointing arrow (→) indicates no change. Greater numbers of upward-pointing arrows indicate greater increases in concentration.
‡
The references shown are selected references related to Covid-19.