In order to assess the effects of tumor downregulation of CD1d on iNKT-mediated antitumor immunity in vivo, we utilized our mouse model of breast cancer metastasis to compare the immune responses of mice implanted with either low metastatic TM40D (CD1d-hi) cells, or highly metastatic TM40D-MB (CD1d-lo) cells. This evidence concerns the gene CD1D and breast cancer.