Single-cell transcriptional profiling reveals anti-CTLA-4 therapy remodels the intestinal immune landscape in inflammation-prone conditions

Aim: Understanding of irAE-driving mechanisms using an irAE animal model Methods: Adult Stat3Δ/Δ (STAT3 is deleted from DCs via the Cre-recombinase system) and Stat3+/+ mice were challenged with B16-OVA melanoma tumors, treated biweekly for 2 weeks with anti-CTLA-4 (clone 9H10) or control IgG. Colonic lamina propria (LP) immune cells were isolated and sorted for live CD45+ cells by fluorescence-activated cell sorting (FACS) 18-19 d after tumor establishment and following completion of therapy. Colonic LP immune cells were subjected to single-cell RNA sequencing (scRNAseq, 10x Genomics). Results: The scRNAseq data, representing 14039 cells from our 4 experimental groups, were concatenated and graphed using unsupervised clustering to identify transcriptionally-related populations. This resulted in elaboration of 19 discrete clusters, including 16 immune and 3 non-immune clusters. Conclusion:This work provides mechanistic insight into irAE development and models for pre-clinical investigation. scRNAseq of CD45+ colonic lamina propria (LP) immune cells purified from melanoma-bearing Stat3+/+ and Stat3Δ/Δ mice (Stat3Δ/Δ mice = Stat3 deleted from CD11c+ cells by the Cre recombinase system) treated with anti-CTLA-4 or control IgG