An immunobiliary single-cell atlas resolves crosstalk of type 2 cDCs and γδT cells in cholangitis

Background and aims The immunobiliary niche serves as a reservoir of tissue-resident immune cells, yet the role of unconventional T cells during cholangitis remains poorly understood. Here, we connect cell state dynamics of type 2 conventional dendritic cells (cDC2) in cholangitis with site-specific γδT17 responses in liver and draining lymph nodes (LN). Methods The 0.1% Diethoxycarbonyl-1,4-Dihydrocollidine (DDC) diet was used to generate an immunobiliary DC- and γδT-enriched mouse liver and LN single-cell RNA-sequencing (scRNA-seq) atlas covering temporal disease dynamics, resolution and cDC2B depletion. cDC2 trajectories were inferred using VarID2 and γδT cell transcription factor (TF) regulon activity was predicted by SCENIC. The human biliary niche was resolved by integrating human liver scRNA-seq data with available spatial transcriptomics data. Functional studies were conducted using Tcrd knockout, Il17a/f knockout and Tcrd reporter mice. Results A disease trajectory of Mgl2+ cDC2B was identified connecting DC maturation, homing and the expression of Il17- inducing genes. Disease progression was associated with numeric exhaustion of mature cDC2B and recruitment of DC precursors. γδT cells were the main Il17 producers and were subtyped into Il17ahigh Scart1+ Vγ6+ and Il17low Scart2+ Vγ4+ populations exhibiting cDC2-directed communication and divergent TF regulon activity. Spatial proximity and conserved molecular interactions of cDC2 and γδT cells were confirmed in human cholangitis. Il17-deficiency resulted in reduced liver fibrosis in mice, while cDC2B depletion attenuated γδT17 cell states. Conclusions In cholangitis, a profibrogenic function of γδT cells is contingent on the induction by peribiliary cDC2B, thereby highlighting relevant disease determinants within the immunobiliary and liver-draining LN niche.