TLR4 and COVID-19: Studies of COVID-19 have evaluated the roles of polymorphisms in ACE2, TMPRSS2, IL-6, ACE, MBL2, AGT, and CCR5. However, the roles of polymorphisms in F2, NLRP3, TLR4, CX3CR, IL1RN, and IL1B in COVID-19 have not been established.