Based on this, the authors proposed the following mechanism: infection with coronavirus causes an increase in IFN levels in the body, which, in turn, promotes the mast cell surface presentation of ACE2 and TMPRSS2, and mast cells become ready to be infected with the virus, which allows the virus to spread further, involving more and more of these cells and stimulating the powerful secretion of their effector molecules. Here, TMPRSS2 is linked to infection.