CD1D and breast cancer: We found that the ability of the CD1d-expressing cells to induce NKT cell cytokine production was reduced by 40–60% following treatment with the cultured supernatant from the breast cancer cell lines, as shown in Figure 5A. Interestingly, in the reverse experiment, when NKT cells were pretreated with the tumor cell supernatants, their function was also reduced (Figure 5B).