Interferon-Gamma-Producing CD8+ Tissue Resident Memory T Cells Are a Targetable Hallmark of Immune Checkpoint Inhibitor-Colitis

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 (T-RM) 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+ T-RM cell activation correlates with clinical and endoscopic ICI-colitis severity. Single-cell RNA sequencing analysis confirms activated CD8(+) T-RM 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(+) T-RM cells are a pathological hallmark of ICI-colitis and a novel target for therapy.

Automated summary

Our study demonstrates that CD8(+) tissue resident memory T (T-RM) cells are the main activated T cell subset in ICI colitis. The pattern of gastrointestinal immunopathology in ICI colitis is distinct from ulcerative colitis at both the immune and epithelial-signaling levels. Activation of CD8+ T-RM cells correlates with clinical and endoscopic severity of ICI colitis.