B-Cell Dysfunction and TLS Biology in iCCA : Gut | May 2026

Introduction

Intrahepatic Cholangiocarcinoma is characterised by a highly desmoplastic and immunosuppressive tumour microenvironment (TME), contributing to poor responsiveness to systemic therapies and immune checkpoint inhibitors. While T-cell biology in iCCA has been extensively investigated, the role of tumour-infiltrating B lymphocytes and tertiary lymphoid structures (TLS) remains poorly defined. This study comprehensively dissected the phenotypic, transcriptional and functional characteristics of B cells within iCCA and evaluated their relationship with chemoimmunotherapy response.

Problem Statement

The immunological contribution of B cells in iCCA is incompletely understood. Whether B cells exert antitumour immunity, become functionally suppressed by the TME, or predict response to immunotherapy remains unclear. Identification of B-cell–mediated immune pathways could open new avenues for biomarker development and therapeutic modulation.

Summary

Using multimodal single-cell technologies, high-dimensional flow cytometry, transcriptomics, imaging mass cytometry and ex vivo coculture systems, the investigators demonstrated that iCCA harbours a profoundly dysfunctional B-cell compartment. B cells were enriched predominantly in peritumoural regions rather than within tumour cores, where they frequently organised into mature tertiary lymphoid structures associated with improved disease-free survival. In contrast, intratumoural B cells were sparse, immature and functionally suppressed.

Single-cell RNA sequencing identified multiple B-cell subpopulations with marked suppression of B-cell receptor signalling, differentiation pathways, inflammatory programs and humoral immune responses within tumours. Tumour-infiltrating B cells demonstrated downregulation of activation-associated genes including CD79B, MYC, CD69 and FOS, alongside increased stress-response signatures. Flow cytometry further confirmed depletion of memory B cells, plasmablasts and activated B-cell subsets within tumours, with enrichment of dysfunctional double-negative and immature phenotypes.

Functionally, patients with iCCA displayed impaired systemic humoral immunity, including reduced circulating IgM, IgA, IgE and later-stage class-switched immunoglobulin subclasses, suggesting defective B-cell maturation and class-switch recombination. Tumour-associated B cells expressed increased immunosuppressive cytokines including IL-10 and TGF-β while exhibiting reduced effector cytokines such as IL-6 and IL-12.

Mechanistically, extensive ligand–receptor interactome analyses revealed that both tumour cells and cancer-associated fibroblasts actively induce B-cell dysfunction through IL-6 and TGF-β–dependent signalling pathways. Ex vivo coculture experiments confirmed that iCCA cells and fibroblasts suppress B-cell maturation, reduce BAFFR expression and promote expansion of exhausted and atypical B-cell subsets. Importantly, combined blockade of IL-6R and TGF-β signalling restored B-cell activation, differentiation and memory/plasmablast generation, highlighting a therapeutically targetable immune axis.

The study additionally demonstrated important predictive implications during chemoimmunotherapy with durvalumab, gemcitabine and cisplatin. Responders exhibited higher frequencies of circulating BAFFR-positive B cells, increased BAFF levels and emergence of hyperexpanded B-cell clonotypes. Elevated BAFFR expression correlated with improved progression-free and overall survival, suggesting that B-cell activation status may function as a clinically relevant predictive biomarker for immunotherapy responsiveness in iCCA.

Overall, this landmark translational study establishes that iCCA is characterised by profound B-cell immunosuppression orchestrated by tumour-stromal interactions. The findings position B cells, BAFFR signalling and TLS maturation as potential biomarkers and therapeutic targets, supporting future strategies aimed at restoring B-cell function and enhancing chemoimmunotherapy efficacy in biliary tract cancers.