Co-expression of CD70 and CD27 is also present on AML [12] and B cell acute lymphoblastic leukemia (B-ALL) blasts [10, 22, 46, 47], on malignant B cells of chronic lymphocytic leukemia (B-CLL) and subtypes including hairy cell leukemia and its prolymphocytic variant [10, 48–51]. Here, CD27 is linked to B-cell chronic lymphocytic leukemia.