Quantitative analysis of mixed chimerism following allogeneic bone marrow transplantation using telomere flow-FISH

Assessment of mixed chimerism is of particular interest for allogeneic bone marrow or peripheral blood stem cell transplantation with reduced-intensity conditioning in order to study contribution of donor-type and host-type lymphohematopoiesis. Because the length of telomere repeat sequences is frequently shorter in leukemic compared to normal hematopoietic cells, this telomere repeat polymorphism might be a useful marker to analyze mixed chimerism in selected patients with short telomeres. Recently, fluorescence in situ hybridization and flow cytometry (flow-FISH) have been shown to be valuable tools to analyze the mean telomere length in hematopoietic cells. Here, we demonstrate in a case study on a patient with chronic lymphocytic leukemia (CLL) that telomere flow-FISH can in principle be exploited to quantitate the amount of donor- and host-type cells for chimerism analysis based on distinct histogram distributions which reflect cell populations with different telomere length.