A genome-wide CRISPR screening identifies targets that drive tolerogenic dendritic cells

Tolerogenic dendritic cells (TolDCs) contribute to immune tolerance and have demonstrated therapeutic potential in early clinical studies of autoimmune diseases. However, the key molecular pathways driving their differentiation and tolerogenic phenotype remain elusive. Here, we investigated the molecular mechanisms underlying the functional status of TolDCs in response to different tolerizing agents and identified CD86 as a consistent and robust marker downregulated in tolerogenic state. CD86 is functionally required for TolDC-mediated suppression of T cell proliferation and cytokine secretion, supporting its use as a surrogate marker of tolerogenic potential. Leveraging CD86 expression as a readout, we performed a genome-wide CRISPR-Cas9 knockout screen and characterized genes associated with TolDC phenotypes. This approach positions UBE2L6 as a regulator of CD86 expression through modulation of an ISG15-USP18-associated pathway, implicating its involvement in tolerogenic functions. These findings describe therapeutically targetable pathways to promote immune tolerance.