CD4 and neoplasm: For example, the immune microenvironment of a large number of PDACs shows increased infiltrates of T-regulatory cells (Tregs) and TAMs with M2 polarisation, as well as myeloid-derived suppressive cells, which block the anti-tumour activities of the effector CD4+ and CD8+ T cells.49–51 Moreover, changes in the immunogenicity of cancer cells (so-called ‘immunoediting’) can lead to immune-resistant clones.44