Besides, the conditional-independence network analysis suggested that apoptotic gene signatures (including BRCA2, CASP3, CASP8, BID, BAK1, and XBP1) significantly increased in plasmacytoid DCs (pDCs) from COVID-19, which is related to low-frequency pDCs and disease severity.67 Another scRNA-seq data was in accordance with this study.68 Generally speaking, pDCs are the major subset of secreted type I IFN (including IFN-α and IFN-β) in response to viral infection.69 This evidence concerns the gene CASP3 and COVID-19.