Deciphering the mechanisms underlying human plasmacytoid dendritic cell function and exhaustion 3178

Abstract Description Type I interferons (IFN-I) are essential to the immune response to viral infection and cancers. Plasmacytoid dendritic cells (pDCs) produce more IFN-I than any other cell type, and consequently pDCs play important roles in viral infections, cancer, and autoimmune diseases. Following viral infection, pDCs initially produce exceptional amounts of IFN-I, but later become functionally “exhausted”, a phenotype described in both mice and human pDCs. A major barrier to studying pDC exhaustion, is the scarcity and short life-span of primary pDCs. To overcome this limitation we established a human in vitro model of pDC exhaustion exploiting the human pDC-like cell line (CAL-1) that when persistently stimulated with either Toll-like receptor (TLR) 7 or TLR9 agonists, phenocopies exhaustion. RNA-seq of exhausted CAL-1 cells revealed exhaustion may be facilitated through the activation of nuclear factor kappa B (NFκB) downstream of TLR7 stimulation. To test this possibility we engineered a novel CRISPR-editable, IFN-B reporter CAL-1 cell line. After individually deleting all NFκB subunits, p50 was identified as a suppressor of IFN-I production in functional cells. This new knowledge can be leveraged to design targeted pDC-based therapies to modulate IFN-I production in multiple human diseases. In addition, the new CRISPR-editable, IFN-B reporter CAL-1 cell line that we have generated provides a valuable resource for future identification of genetic and chemical pDC regulators. Funding Sources Supported by NIH grants AI145314, AI081923, and AI113923 Topic Categories Antigen and Dendritic Cell Processing, Presentation, and Biology (AGDC)