Even though the protective function of the serine protease inhibitor SerpinA1 (alpha1-antitrypsin) in COVID-19 is controversial, in general, SerpinA1 inhibits CatG, NE, PR3, and TMPRSS2, and is known to be typically upregulated in response to managing inflammation and tissue damage, which is important for the immune system to return to homeostasis [29,30]. Here, TMPRSS2 is linked to COVID-19.