To evaluate CD8+ T-cell exhaustion in 4T1 breast tumour-bearing mice, we examined the level of IR mRNAs, including PD-1, TIM-3, BTLA and exhausted T-cell-associated transcriptional factor Foxp1 using reverse transcription quantitative polymerase chain reaction (RT–qPCR). The gene discussed is CD8A; the disease is breast neoplasm.