Group 1 CD1 molecules are expressed only by mature hematopoietic cells6, and their expression is elevated in leukemia and lymphoma cells; indeed, CD1c is detected on all the blasts of 54% of adult and 45% of pediatric AML patients, and on all the blasts of 71% of adult and 26% of pediatric B cell acute lymphoblastic leukemia10. Here, CD1A is linked to leukemia.