TLR7 escapes the XCI in female B cell, resulting in the higher expression levels in women than in men.47 Young men with severe COVID-19 were found to carry the four nucleotide deletion in TLR7 (c.2129_2132del; pGln710Argfs*18), while the affected family members carried only one missense variant on TLR7 (c.2383G>T; pVal795Phe).37 This evidence supports the potential role of TLR7 in the male-biased mortality in severe COVID-19 patients (Fig. 5b). Here, TLR7 is linked to COVID-19.