SERPINA1 and COVID-19: Alpha-1-antitrypsin (AAT) is a 52 kDa glycoprotein synthesized in the liver with high concentrations at plasma level, which possesses anti-inflammatory functions (inhibition of NF-kB, IL-8), as well as inhibiting serine proteases such as metalloproteinase 17 (ADAM17) and transmembrane surface serine protease 2 (TMPRSS2), which are crucial for entry of SARS-CoV-2 into the host cell and associated with poor disease prognosis, It is found at low concentrations in patients with severe COVID-19 [302,303,304,305].