CD27 and breast cancer: Previously, we identified CD39+Vδ T cells as the dominant Tregs in colon cancer.12 Here, we aimed to explore whether there is a specific subtype of Vδ1+ T cells in BC that plays a major immunosuppressive role by evaluating the expression of regulatory immune cell markers (CD27, CD25, CD39, CD73, CTLA-4, CD122 and FoxP3) on Vδ1/2+ T cells isolated from PBHDs and Vδ1/2+ T cells isolated from peripheral blood of breast cancer patients (PBBCs), normal breast tissues (NT) and breast cancer (BC) tissues (Fig. 2a–d, Supplementary Fig. S3).