In contrast, regulatory T (Treg) cells suppress the function of conventional T (Tconv) cells including CD4+ and CD8+ T cells and although this function is required to prevent unwanted autoimmune and allergic inflammation, it is now known that Treg cells play a critical role in suppressing immune responses in cancer.3, 4 Treg cells also have a number of non‐classical functions, some of which may directly influence tumour cell biology, or act in a tissue‐specific manner. Here, CD4 is linked to cancer.