Research Center for Transplant Immunology, Institute of Hematology and Medical Oncology 'Seràgnoli', University of Bologna, Bologna, Italy

Correspondence to: Dr D Rondelli, Istituto di Ematologia e Oncologia Medica 'Seràgnoli', Università di Bologna, Policlinico S Orsola-Malpighi, via Massarenti, 9, 40138 Bologna, Italy

TH2-inducing dendritic cells (DC2) are commonly identified as negative for lineage markers and positive for HLA-DR and CD123 expression. More recently, normal blood DC2 were shown also to be positive for BDCA-2 and BDCA-4 antigens. The aim of this study was to evaluate whether BDCA-2 expression on DC2 is impaired in patients undergoing an allogeneic hematopoietic stem cell transplantation (HSCT) and in healthy donors treated with G-CSF for HSC mobilization. Flow cytometry assays for DC2 detection using either a triple staining with anti-HLA-DR PerCP, anti-Lin⁺ anti-CD34 FITC and anti-CD123 PE monoclonal antibodies (mAbs), or a double staining with anti-HLA-DR PE and anti-BDCA-2 FITC mAbs were compared in blood samples from patients who underwent an allogeneic HSCT (n = 30) or from healthy donors before (n = 11) and after (n = 8) G-CSF mobilization, as well as in healthy donors' leukapheresis products (n = 12) or bone marrow (n = 4). Staining of BDCA-2⁺ cells with other markers such as anti-CD38, anti-CD54 and anti-CD58 were also performed. Median values of CD123⁺ DC2 and BDCA-2⁺ DC2 were not statistically different in the blood of patients previously treated with chemotherapy, nor in the blood or bone marrow of heathy donors. Also, a 5 day G-CSF treatment did not affect BDCA-2 or adhesion molecule expression on healthy donors' blood DC2 significantly. A correlation between all the results (n = 65) obtained with the two assays was demonstrated in a linear regression curve (r = 0.914) (P = 0.00001). BDCA-2 is a marker highly specific for DC2 that is not downregulated by chemotherapy or G-CSF treatment. Therefore, the anti-BDCA-2 mAb can be efficiently combined with other mAbs and used in studies addressing the role of DC2 in the allogeneic HSCT setting.

Bone Marrow Transplantation (2002) 29, 887-891. DOI:10.1038/sj/bmt/1703569

bone marrow transplantation; PBSC; G-CSF; DC2; BDCA-2; CD123