For example, in two melanoma studies, favourable responses to immune checkpoint inhibitors are associated with either higher densities of CD8+ tumour-infiltrating lymphocytes (TILs) within a distance of 20 μm of melanoma cells5 or a higher proportion and closer proximity of (proliferating) antigen-experienced CD8+ T cells to the tumour cells6. This evidence concerns the gene CD8A and neoplasm.