Monitoring of minimal residual disease after HLA-mismatched allogeneic hematopoietic stem cell transplantation using six-color based HLA-Flow method in pediatric acute leukemia.

: HLA-Flow is a flow cytometry-based method using anti-HLA antibodies against mismatched HLA alleles combined with the antibodies against antigens expressed on leukemic cells. It is a sensitive assay to determine minimal residual disease (MRD) after HLA mismatched hematopoietic stem cell transplantation (HSCT). In this study, we report the results of our HLA-Flow using six-color based multicolor fluorescence-activated cell sorting for HLA-mismatched HSCT. We performed HLA-Flow monitoring after HLA mismatched HSCT from July 2013 to July 2016 in nine patients (three with acute lymphoblastic leukemia, five with acute myeloid leukemia, and one with therapy-related acute myeloid leukemia) for MRD monitoring. We detected a relapse after HSCT in three of the nine patients, two of them at MRD levels. HLA-Flow is a sensitive, fast, and inexpensive method for the detection of MRD in patients with HLA-mismatched HSCT.