Circulating pDCs were observed with decreased levels of CD45RA (Fig. 3 F and G), while pDCs in BAL were enriched for cytokine and chemokine signaling pathways and further presented with reduced gene expression of LAMP5, known to be down-regulated in response to TLR9 stimulation and type I IFN signaling (28), in severe COVID-19 patients (Fig. 3I). The gene discussed is TLR9; the disease is COVID-19.