CD4 and neoplasm: Indeed, the metabolic signature of infiltrating immune cells, i.e., CD4+, CD8+ cells, M1/M2 macrophages, natural‐killer cells (NK cells), dendritic cells (DCs) and myeloid‐derived suppressor cells (MDSCs), is shaped not only by cytokines and chemokines but also by several metabolites released by tumour and tumour‐associated cells, such as kynurenine, arginine and adenosine [10, 11].