Altered surface phenotype of dendritic cells and their subsets in patients with COVID-19. DCs subsets: cDC1s carry BDCA-3 (CD141), Clec9A, CADM1, BTLA, and CD26 (are capable of cross-presentation of antigens to cytotoxic T-lymphocytes and polarization of ‘naive’ Th cells to Th1); cDC2s are CD1c+ (as well as FcεR1+SIRPA+; are capable to initiate responses mediated by various Th cell subsets) [30]; cDC2 can be subdivided into CD5+ DC2 and CD5− DC3 (consists of several subsets); finally, pDC are CD123+CD11c– and play a crucial role in antiviral response by secreting type I interferons and IL-12 (polarization of Th0 to Th1) [31]. Functional activity of almost all DC subsets can be reduced in severe COVID-19 cases (low levels of MHC molecules and limited costimulatory signaling (a decreased frequency of CD80 and CD86).