TLR7 and COVID-19: In addition, variants in the tyrosine kinase 2 (TYK2) gene [23], in the Toll-like receptor 7 (TLR7) gene [26], and the interferon-alpha/beta receptor 2 (IFNAR2) gene [19,23] which play crucial roles in immune response regulation, pathogen recognition pathways, and interferon signaling respectively, have been reported to be linked to severe COVID-19 outcomes.