In response to in vitro stimulation with ligands for TLR3, TLR4, TLR7, or TLR8, the key populations of DCs from COVID-19 patients (i.e., pDC, cDC1, and cDC2) expressed less CD80, CD86, CCR7, and HLA-DR than the cells from corresponding populations of apparently healthy volunteers [21]. This evidence concerns the gene MPPE1 and COVID-19.