CD44 and leukemia: Based on the finding that leukemia cells efficiently compete with HSC under the condition of myeloablation and reconstitution [28,29], we here asked whether anti-CD44 also interferes with hematopoiesis in the non-compromised leukemia-bearing host and whether such interference could be prevented by replacing anti-panCD44 with a CD44 variant isoform-specific antibody.