This project is focused on uncovering the key immune cell populations that drive response to immunotherapy and developing ways to monitor them in real time. By combining single-cell and spatial profiling of tumours and tumour-draining lymph nodes with longitudinal blood samples, we aim to track the expansion and activity of tumour-reactive T cell clones during and after treatment. The goal is to identify immune response determinants that can serve as dynamic biomarkers, enabling clinicians to monitor response without relying solely on imaging, and to guide treatment decisions more precisely for patients with melanoma.