Fig. 2

The human circulating pDC subsets. Human pDCs are defined as Lin⁻ CD11c⁻ CD123/IL3R⁺ BDCA-2/CD303⁺ BDCA-4/CD304⁺ cells and designated to IFN-α production. Upon stimulation with TLR7/9 ligands, three human pDC subpopulations were identified as PD-L1⁺CD80⁻ pDCs (P1) specialized in I-IFN production, PD-L1⁻CD80⁺ pDCs (P3) specialized in adaptive immune functions, and PD-L1⁺CD80⁺ pDCs (P2) showing both innate and adaptive immune functions. In unstimulated/basal conditions, no pDCs subsets have been detected. The CD2⁺ pDCs subset most likely corresponds to a new DC cluster, named AS-DC, that is identified as AXL⁺LYZ⁺SIGLEC6⁺ DCs exerting regulatory functions, such as inducing T cells activation and expansion. The expression of AXL and LYZ was also previously observed on the CD5⁺CD81⁺ subset among CD2⁺ pDCs. Created with BioRender.com