IL-10 is a well-known immunosuppressive cytokine, which is secreted by tumour cells and Tregs among other immune cells and has an important role in tumour immunosurveillance.60 On the other hand, IFNγ is a pleiotropic molecule with antitumour effects, which is produced primarily by cytotoxic CD8+ T lymphocytes and NK cells.61 H4R stimulation enhanced IL-10 while decreased IFNγ levels in tumour conditioned medium of WT mice, suggesting an immunosuppressive role of H4R in the context of 4T1 breast cancer model. The gene discussed is CD8A; the disease is breast cancer.