Supplementum 302: Abstracts of the annual meeting of the Swiss Society of Allergy and Immunology and of the Swiss Autoimmune Liver Disease Meeting (Lugano, August 27-28, 2026)

Abstract

Introduction and Aim of the study: Colorectal cancer (CRC) is the second-leading cause of cancer deaths worldwide.During carcinogenesis, alteration of the gut epithelial barrier allows the translocation of gut bacteria to the tumor tissue and their interaction with immune cells.Infiltration by T cells is associated with improved survival, but their interplay with gut bacteria has not been fully investigated.We previously identified a panel of bacteria whose abundance in CRC tissues correlates with T cell infiltration.In this work, we investigated the capacity of these bacteria to induce T cell-mediated anti-tumor responses.Design and Methods: Peripheral blood mononuclear cells from healthy donors or CRC patients were cultured with gut bacteria of interest and assessed for proliferation based on CFSE dilution.Phenotypes and functionality of proliferating T cells were assessed by FACS.CRC and adjacent normal tissue biopsies were processed to obtain single-cell suspensions.Phenotypes and signatures of tumor-infiltrating T cells were assessed by FACS and single-cell RNA-sequencing. Results and Conclusions: Proliferating cells to bacteria mostly consisted of CD4-CD8-double negative T cells expressingVδ2+ γδTCRs.Expanded Vδ2+ γδT cells formed immunological synapses and showed BTN3A1-independent tumor cell killing.Tumor-infiltrating Vδ2+ γδT cells are detected within CRC tissues, and their transcriptomes partially overlapped with those expanded upon bacterial stimulation from peripheral blood.Their anti-tumor potential is currently under evaluation.