Umbilical cord blood CD34 + cell– derived progeny produces human leukocyte antigen–G molecules with immuno-modulatory functions Marina Buzzi a , Francesco Alviano a , Diana Campioni b , Marina Stignani c , Loredana Melchiorri c , Antonella Rotola d , Pierluigi Tazzari a , Francesca Ricci a , Cristiana Vaselli a , Adriana Terzi a , Pasquale P. Pagliaro a , Antonio Cuneo b , Francesco Lanza e , Andrea Bontadini a , Olavio R. Baricordi c , Roberta Rizzo d, * a Immunohaematology and Transfusion Medicine Service, S.Orsola-Malpighi Hospital, University of Bologna, Bologna, Italy b Department of Biomedical Sciences and Advanced Therapies, Haematology Section, Ferrara Hospital, Ferrara, Italy c Section of Medical Genetics - Department of Experimental and Diagnostic Medicine, University of Ferrara, Ferrara, Italy d Section of Microbiology, Department of Experimental and Diagnostic Medicine, University of Ferrara, Ferrara, Italy e Haematology and Bone Marrow Transplantation Centre, Cremona Hospital, Cremona, Italy ARTICLE INFO Article history: Received 9 August 2011 Accepted 1 December 2011 Available online 8 December 2011 Keywords: CD34 + cell HLA-G Immunoregulation Umbilical cord blood Transplant ABSTRACT Human umbilical cord blood units (UCBs) are an alternative source in allogeneic-stem-cell transplantation. Human leukocyte antigen (HLA)–G is a tolerogenic molecule with a possible implication in UCB immuno- regulatory effect. HLA-G expression was observed in UCB myeloid and plasmacytoid dendritic cells; in contrast, CD34 + cells did not produce this molecule. CD34 + cells are primitive hematopoietic progenitor cells that are present in UCB and are necessary for long-term engraftment via production of immunoregulatory molecules and a hematopoietic progeny that supports cellular recovery. The role of these cells in UCB transplantation needs further evaluation of HLA-G expression in CD34 + cells and their hematopoietic progeny. We confirmed the absence of HLA-G expression in CD34 + cells, whereas CD34 + -derived progeny secreted HLA-G molecules and expressed HLA-G mRNA in in vitro cultures. Furthermore, soluble HLA (sHLA)–G molecules purified from the culture supernatants of CD34 + -derived progeny were able to suppress lymphoproliferative response in an HLA-G dose-dependent manner. Overall these results identify CD34 + - derived hematopoietic progeny as producers of HLA-G molecules and support a role of this antigen as an immuno-modulatory factor in UCB.  2012 American Society for Histocompatibility and Immunogenetics. Published by Elsevier Inc. All rights reserved. 1. Introduction Human umbilical cord blood (UCB) has been used clinically for more than 20 years as an alternative cell source to bone marrow and granulocyte colony-stimulating factor mobilized peripheral blood progenitor cells for hematopoietic stem cell transplantation [1–3]. First used in transplants in children, UCBs induce a general- ized reduction of graft-versus-host disease (GvHD) incidence and severity and a lower necessity of a stringent human leukocyte antigen (HLA) compatibility [4–8]. The immunoregulatory properties of UCBs are partly related to the presence of soluble molecules as indoleamine-2,3-dioxigenase (IDO) [9]. IDO is an immuno-modulatory enzyme involved in the inhibition of cell proliferation, including that of activated T cells. Interestingly, IDO functions are commonly complementary with that of another molecule: human leukocyte antigen (HLA)–G [10]. HLA-G molecules are HLA Ib antigens characterized by a low allelic polymorphism (46 alleles) in comparison with HLA class Ia mole- cules, and a physiologic tissue distribution restricted to cytotro- phoblasts, thymus, and immuno-previleged sites. Furthermore, the mRNA alternative splicing at gene level can generate different membrane-bound (HLA-G1, -G2, -G3, and -G4) and soluble (HLA- G5, -G6, and -G7) isoforms [11]. The proteolytic cleavage of surface HLA-G1 isoform generates the soluble HLA-G1 form. HLA-G mole- cules, in both membrane-bound and soluble (sHLA-G) isoforms, are mediators of immuno-suppressive functions toward innate and adaptive immune responses by their interaction with the inhibitory receptors leukocyte immunoglobulin-like receptor (LILRB)–1 (leukocyte immunoglobulin-like receptor, subfamily B) (immunoglobulin-like transcript [LT]–2/CD85j) and LILRB2 [ILT-4/ CD85d], CD8 -chain, killer immunoglobulin-like receptor 2DL4 (KIR2DL4/CD158d) [12]. HLA-G molecules are able to induce ap- optosis of CD8 + T cells, inhibit natural killer (NK) cell activity and allo-specific CD4 + T cell proliferation, enhance the production of regulatory CD4 + T cells and suppress the differentiation of den- dritic cells [12]. * Corresponding author. E-mail address: rbr@unife.it (R. Rizzo). Human Immunology 73 (2012) 150-155 Contents lists available at SciVerse ScienceDirect 0198-8859/$36.00  2012 American Society for Histocompatibility and Immunogenetics. Published by Elsevier Inc. All rights reserved. doi:10.1016/j.humimm.2011.12.003