Efficient discrimination of functional hematopoietic stem cell progenitors for transplantation by combining alkaline phosphatase activity and CD34+ immunophenotyping

Alkaline phosphatase (ALP) is a membrane-associated hydrolase enzyme with dimeric structure that catalyzes phosphate esters, optimally at alkaline pH. ALP has a focus of interest, since this enzyme is highly expressed in primitive stem cells, such as progenitor cells, non-differentiating cells, and primordial cells. We previously adapted a fluorescent microscopy-based assay for quantifying ALPhigh and ALPlow cells by flow cytometry in combination with immunophenotyping. Our method uses a minimal sample perturbation approach, avoiding the use of erythrocyte lysing solutions and washing steps, and offering opportunities to combine live cell response and functional assessment with cell immunophenotyping, while minimizing sample preparation effects on the cell biology. Here we provide a detailed experiment protocol to determine alkaline phosphatase activity in CD34+ hematopoietic stem cells from blood and apheresis products obtained from patients involved in a stem cell mobilization process for allo- or auto-transplant. This study may provide the early detection of progenitors at different levels of differentiation and therefore, relate this information to long-term engraftment in hematopoietic stem cell transplants.