In this study, we found that the ratio of CD4+ and CD4+/CD8+ cells in the research group was significantly higher than these of the control group, while the ratio of CD8+ cells was lower than that of the control group at 1 h during operation and 24 h after operation, indicating dexmedetomidine can significantly reduce anesthesia-induced immunosuppression in patients undergoing MRM for breast cancer. This evidence concerns the gene CD8A and breast cancer.