Consistent with the overexpression of IRs in human melanoma, lymphoma, hepatocellular carcinoma and gastric cancer [39–41], our results show that mRNAs encoding PD-1, TIM-3, BTLA and Foxp1 are also upregulated in CD8+ T cells isolated from spleens of mice-bearing mouse 4T1 breast tumours. Here, BTLA is linked to lymphoma.