IFITM1 and viral infectious disease: For example, we found the expression of IFITM3 was not upregulated in IFITM1 KO hESCs in which HERVs were increased, suggesting a feedback loop between HERV expression and IFITM1‐mediated defense of viral infection and also suggesting that other IFITM proteins may not respond to the upregulated HERVs, though we could not state that they do not regulate HERVs in hESCs.