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BACKGROUND & AIMS: The pathogenesis of immune checkpoint inhibitor (ICI)-colitis remains incompletely understood. We sought to identify key cellular drivers of ICI-colitis and their similarities to idiopathic ulcerative colitis, and to determine potential novel therapeutic targets. METHODS: We used a cross-sectional approach to study patients with ICI-colitis, those receiving ICI without the development of colitis, idiopathic ulcerative colitis, and healthy controls. A subset of patients with ICI-colitis were studied longitudinally. We applied a range of methods, including multiparameter and spectral flow cytometry, spectral immunofluorescence microscopy, targeted gene panels, and bulk and single-cell RNA sequencing. RESULTS: We demonstrate CD8+ tissue resident memory T (TRM) cells are the dominant activated T cell subset in ICI-colitis. The pattern of gastrointestinal immunopathology is distinct from ulcerative colitis at both the immune and epithelial-signaling levels. CD8+ TRM cell activation correlates with clinical and endoscopic ICI-colitis severity. Single-cell RNA sequencing analysis confirms activated CD8+ TRM cells express high levels of transcripts for checkpoint inhibitors and interferon-gamma in ICI-colitis. We demonstrate similar findings in both anti-CTLA-4/PD-1 combination therapy and in anti-PD-1 inhibitor-associated colitis. On the basis of our data, we successfully targeted this pathway in a patient with refractory ICI-colitis, using the JAK inhibitor tofacitinib. CONCLUSIONS: Interferon gamma-producing CD8+ TRM cells are a pathological hallmark of ICI-colitis and a novel target for therapy.

Original publication




Journal article



Publication Date





1229 - 1244.e9


Checkpoint Colitis, Immunotherapy Colitis, Tofacitinib, Ulcerative Colitis, CD8-Positive T-Lymphocytes, CTLA-4 Antigen, Case-Control Studies, Colitis, Colitis, Ulcerative, Colon, Cross-Sectional Studies, Gene Expression Profiling, Humans, Immune Checkpoint Inhibitors, Immunologic Memory, Interferon-gamma, Longitudinal Studies, Lymphocyte Activation, Memory T Cells, Phenotype, Piperidines, Programmed Cell Death 1 Receptor, Prospective Studies, Pyrimidines, RNA-Seq, Single-Cell Analysis, Transcriptome