Enumeration of bone marrow plasmacytoid dendritic cells by multiparameter flow cytometry as a prognostic marker following allogeneic hematopoietic stem cell transplantation

Abstract Plasmacytoid dendritic cells (pDCs) promote tolerance in solid organ transplants and hematopoietic stem cell transplantation (HSCT). pDCs originate from CD34 + hematopoietic progenitors. Following allogeneic hematopoietic stem cell transplant (allo-HSCT), pDC reconstitution in the BM and PB gradually attain levels similar to those in healthy individuals. We have investigated the recovery of pDC following allo-HSCT as a means to predict successful marrow engraftment. We retrospectively studied immune reconstitution of pDC in the BM of 48 patients following allo-HSCT for initial diagnoses of leukemia or other malignancies. Multi-parameter flow cytometry was used to detect the CD45 +  CD123 bright HLA-DR + CD4 low pDCs in BM aspirates at 2–14 months (median 6 months) post allo-HSCT. Percentages of pDCs were analyzed along with engraftment, acute graft-versus-host disease (aGVHD), event-free survival, relapse and death over a period of up to 39 months (median 30) following HSCT. We report that higher levels of pDCs in the BM post-HSCT are associated with successful engraftment, less severity of aGVHD, lower relapse rate, higher event-free survival and overall survival ( P value