KLRB1 and breast carcinoma: We show not only a significantly greater efflux of daunorubicin from MAIT cells compared to other cell subsets, in line with data showing efflux by effector memory CD161++CD8+ T cells [16], but also directly demonstrate MDR1‐mediated protection from apoptosis for the first time, previously correlated only with preferential survival in patients receiving chemotherapy for breast cancer over other lymphocyte subsets [17].