In these studies, iNKT cell-deficient mice generated by the deletion of the genes encoding the invariant TRAJ18 TCR chain (Jα18−/−) or CD1d (CD1d−/−) were challenged with methylcholanthrene or crossed with tumor-predisposing genetically engineered strains, resulting in earlier onset and higher incidence of cancer with reduced survival. The gene discussed is CD1D; the disease is cancer.