Establishing a Population-Based HLA-Antibody Panel for Flow Cytometric Monitoring of Chimerism in HLA-Haploidentical Stem Cell Transplantation.

Determining the chimerism in stem cell transplantation (SCT) is important in the monitoring of engraftment. Conventional monitoring methods such as short tandem repeat polymerase chain reaction (STR-PCR) are labor intensive and difficult in showing the dynamics of cell subpopulations. In HLA-haploidentical SCT, flow cytometric analysis using anti-HLA antibody for the mismatched HLA can be useful in observing changes of cell subpopulations and determining chimerism. We designed a specific panel of HLA antibody reagents for the Korean population, and verified its clinical application in flow cytometric monitoring of chimerism after haploidentical stem cell transplantation. A total of 12 anti-HLA-A, -B-antibodies were selected, which could cover 82.5% of HLA-A and 16.5% of HLA-B in Korean population. This HLA panel distinguished donor and recipient cells in 22 of 23 HLA-haploidentical SCT cases. In one case, the patient had HLA-A02/A24, B48/B61 while the donor had HLA-A02/A33, B44/B48. The donor type HLA-B44(+) and CD3(+) T cells, and HLA-B44(+) and CD56(+) NK cells were seen at day 14 and day 8, respectively. Increased HLA-B*44(+) cells throughout the study period indicated the engraftment of donor stem cells. We were able to design a population specific panel of HLA-antibodies, and verified that flow cytometric analysis using HLA antibody for the detection of chimerism in HLA-haploidentical SCT was a simple and sensitive monitoring technique. This method allowed us to observe the dynamic changes in cell subpopulations after HLA-haploidentical SCT. Flow cytometric analysis can be considered as a strong tool for the monitoring of engraftment in HLA-haploidentical SCT.