These therapies aim to improve the potency of the anti-tumour response and/or to increase the frequency of tumour-infiltrating CD4+ and CD8+ T cells, often by restoring the balance of immunosuppressive Tregs to anti-tumoural CD4+ and CD8+ T cells.1 While studies designed to either inhibit or deplete regulatory Tregs have shown promise at the pre-clinical stage, developing clinically-relevant Treg-specific therapies have proved more challenging. This evidence concerns the gene CD4 and neoplasm.