Consistent with the hypothesis that the reduced efficacy of CpG ODN against primary ALL was a consequence of low antigen burden, we repeated the experiment using CD1d-deficient mice as recipients, a setting where the presence of CD1d on the surface of ALL blasts from Eμ-ret transgenic BALB/c mice would serve as a novel antigen. This evidence concerns the gene CD1D and acute lymphoblastic leukemia.