Assessment of lineage-specific chimerism after allogeneic stem cell transplantation

Introduction Donor lineage-specific chimerism of hematopoietic cells enables very precise monitoring of engraftment in selected cell lines after allogeneic stem cell transplantation (allo-SCT). Materials and methods The study group consisted of 12 acute leukemia patients who underwent allo-SCT in the Department of Hematology and Bone Marrow Transplantation in Katowice, Poland. Lineage-specific chimerism was assessed in B cells (CD19+ CD38−/+), plasma cells (CD19+ CD38++), T cells (CD3+ or CD7+ CD56−), monocytes (CD14+), and immature progenitor cells deriving from myeloid line (CD34+CD19). We also assessed erythrocyte chimerism by flow cytometry. Results All patients engrafted. 8 out of 10 patients presented normal donor hematopoiesis. Lineage specific chimerism in these patients corresponded with chimerism analysis in unsorted material and with undetectable minimal residual disease (MRD). Relapse of the underlying disease was diagnosed in 2 patients. In both cases loss of donor chimerism occurred in leukemia specific cell line and corresponded with detectable MRD. One patient with secondary graft failure presented decreasing lineage specific chimerism in all subpopulations, with negative MRD status. In 10 patients normal hematopoiesis of donor-origin was assessed by flow cytometry. In one case no donor-derived erythrocytes were detected and the diagnosis of pure red cell aplasia was set. Conclusions Lineage specific chimerism as a method of high sensitivity and specificity allows for precise assessment of donor chimerism especially in clinically ambiguous situations. Assessment of erythrocyte chimerism by flow cytometry is a reliable method of monitoring erythroblastic line engraftment. Presented results are preliminary and the study is being continued.