In order to elucidate the specific roles of CD1d-restricted NKT cells in our model of breast cancer, we utilized CD1d KO (type I and type II NKT cell deficient), Jα18 KO (type I NKT cell deficient) and RAG2 KO (B and T cell deficient) mice to compare tumor growth and metastasis rates between our CD1d-lo and CD1d-hi tumor cells. The gene discussed is RAG2; the disease is neoplasm.