CD 45 RA , a specific marker for leukaemia stem cell sub‐populations in acute myeloid leukaemia

Chemotherapy resistant leukaemic stem cells ( LSC ) are thought to be responsible for relapses after therapy in acute myeloid leukaemia ( AML ). Flow cytometry can discriminate CD 34 + CD 38 − LSC and normal haematopoietic stem cells ( HSC ) by using aberrant expression of markers and scatter properties. However, not all LSC can be identified using currently available markers, so new markers are needed. CD 45 RA is expressed on leukaemic cells in the majority of AML patients. We investigated the potency of CD 45 RA to specifically identify LSC and HSC and improve LSC quantification. Compared to our best other markers ( CLL ‐1, also termed CLEC 12A, CD 33 and CD 123), CD 45 RA was the most reliable marker. Patients with high percentages (>90%) of CD 45 RA on CD 34 + CD 38 − LSC have 1·69‐fold higher scatter values compared to HSC ( P