PD-L1 regulates inflammatory programs of macrophages from human pluripotent stem cells

Abstract

Programmed death ligand 1 (PD-L1) serves as a pivotal immune checkpoint in both the innate and adaptive immune systems. PD-L1 is expressed in macrophages in response to IFNγ. We examined whether PD-L1 might regulate macrophage development. We established PD-L1 KO (<i>CD274</i> ^<i>-/-</i> ) human pluripotent stem cells and differentiated them into macrophages and observed a 60% reduction in CD11B⁺CD45⁺ macrophages in <i>CD274</i> ^<i>-/-</i> ; this was orthogonally verified, with the PD-L1 inhibitor BMS-1166 reducing macrophages to the same fold. Single-cell RNA sequencing further confirmed the down-regulation of the macrophage-defining transcription factors <i>SPI1</i> and <i>MAFB</i> Furthermore, <i>CD274</i> ^<i>-/-</i> macrophages reduced the level of inflammatory signals such as NF-κB and TNF, and chemokine secretion of the CXCL and CCL families. Anti-inflammatory TGF-β was up-regulated. Finally, we identified that <i>CD274</i> ^<i>-/-</i> macrophages significantly down-regulated interferon-stimulated genes despite the presence of IFNγ in the differentiation media. These data suggest that PD-L1 regulates inflammatory programs of macrophages from human pluripotent stem cells.