Bile duct cancer is a deadly disease. Immunotherapy is part of first-line therapy for advanced bile duct cancer, but response rates are low. The network of innate immune cells and bacteria in bile duct tumours and their ability to influence the course of the disease is largely unknown. This project aims to understand the interplay of bacteria and innate lymphoid cells (ILCs) in the tumour and the tumour environment. The network of ILCs and bacteria in bile duct cancer is investigated in order to identify processes that can be used therapeutically. This information should help to optimise the immunotherapy of bile duct cancer.