APP and infection: Our present work revealed that SARS-CoV-2 infected the alveolar target cells AT1/AT2 to result in immune activation and release a large number of inflammation-related ligands and receptors (such as ANXA1_FPRs, CXCLs_CXCRs, CD74_APP, CD74_COPA, CCL5_CCRs) (Figs. 3 and 6H), which could further bind to their receptors on free myeloid cells in the lung cavity to rapidly induce their enrichment to the infection site.