Work

974 Integrated multimodal profiling reveals conserved type II interferon signalling, ectopic lymphoid structure formation, and actionable inflammatory endotypes in cutaneous immune-related adverse events

Year: 2026

Type: conference-abstract

Abstract: Background Immune checkpoint inhibitors (ICIs) have transformed cancer treatment but frequently cause immune-related adverse events (irAEs) in healthy tissues. Cutaneous irAEs (cirAEs) are the most common toxicity, yet their molecular mechanisms remain poorly understood, leaving treatment reliant on corticosteroids that may compromise anti-tumour efficacy. We applied single-cell RNA sequencing, spatial transcriptomics, and multiplex immunofluorescence with matched blood proteomic and immune receptor repertoire profiling to define the molecular basis of cirAEs.Methods Paired skin biopsies were collected from 8 patients with cirAEs, 3 on-treatment controls, and 4 untreated controls. Samples underwent 10x Genomics single-cell RNA/TCR sequencing, histology, 6-plex multiplex immunofluorescence, and (in two cases) Visium HD spatial transcriptomics. Matched longitudinal blood samples were profiled using the Alamar NULISAseq 250-plex inflammation panel. Matched longitudinal whole blood RNA underwent bulk TCR sequencing using the Cellecta DriverMap Human RNA kit.Results cirAEs showed expansion of proliferating and effector T cells, B-cells, inflammatory macrophages and fibroblasts, with upregulation of IFNγ-response, B-cell, and alarmin genes, alongside loss of barrier maintenance genes. We identified a cirAE-associated population of proliferating CXCL13 +, IL21+, CXCR5- T peripheral helper (Tph) cells indicating the formation of ectopic lymphoid structures (ELSs). This was confirmed by multiplex immunofluorescence and Visium HD spatial transcriptomics, which demonstrated organised T- and B-cell aggregates with class-switched plasma cells. Pseudobulk analysis recapitulated conserved IFNγ- and ELS-driven inflammatory programmes across all cases but found marked inter-patient heterogeneity characterised by distinct Th1, Th2, Th17, and eosinophilic inflammatory endotypes. Longitudinal plasma proteomics validated systemic upregulation of core IFNγ- and ELS signatures as well as matching accessory inflammatory endotypes. Tissue TCR sequencing demonstrated further inter-patient heterogeneity in clonal dominance and matching longitudinal blood TCR profiling cross-validated this through expansion and subsequent shrinkage of shared cirAE-associated clones.Conclusions Deep multimodal profiling of cirAEs in tissue and blood reveals dysregulation across T-cell, non-T immune cell, and stromal cell populations. cirAEs share a conserved type II interferon-driven inflammatory programme and are characterised by ectopic lymphoid structures associated with a previously unrecognised proliferating Tph cell population and mature class-switched B-cell responses. Beyond this, cirAEs feature striking heterogeneity of accessory inflammatory signatures and TCR clonal repertoires. Matching core immune programmes are known to be enriched in tumours responding to ICI, 1 2 suggesting that our findings provide a mechanistic link between irAEs and anti-tumour immunity. Our work highlights that therapeutic strategies should seek to preserve core interferon- and B-cell-mediated immune responses and instead align targeted immunosuppression to dominant accessory inflammatory endotypes.References Cabrita R, et al. Tertiary lymphoid structures improve immunotherapy and survival in melanoma. Nature 2020;577:561–565 (2020).House IG, et al. Macrophage-derived CXCL9 and CXCL10 are required for antitumor immune responses following immune checkpoint blockade. Clin Cancer Res. 2020;26:487–504.Ethics Approval Samples and patient data were derived from the EXACT (understanding immune related toxicities through multifaceted profiling) prospective observational cohort study ( NCT05331066). EXACT is sponsored by the Royal Marsden Hospital and was approved by the UK West Midlands – Black Country Research Ethics Committee of the National Health Service Health Research Authority (Ref 21/WM/0251). All participants provide written informed consent prior to study entry.

Source: Journal for ImmunoTherapy of Cancer

DOI: 10.1136/jitc-2026-sitc2026.0974