Notably, the LAD2, LUVA, and HMC-1 mast cell lines were found to be susceptible to infection by human coronavirus 229E (HCoV-229E), which utilizes APN as its receptor, and human coronavirus NL63 (HCoV-NL63), which utilizes ACE2 as its receptor (Fig. 1B). This evidence concerns the gene ACE2 and infection.