118 TRANSFUSION Volume 46, January 2006 Blackwell Science, LtdOxford, UKTRFTransfusion0041-11322006 American Association of Blood Banks January 2006461118125Original ArticleCD34+ CELLS FROM WHOLE-BLOOD FILTERSIVANOVIC ET AL. ABBREVIATIONS: CFC(s) = colony-forming cell(s); LDF(s) = leukodepletion filter(s); MGDF = megakaryocyte growth and development factor. From the French Blood Establishment Aquitaine-Limousin, Bordeaux, France; Drexel University, Philadelphia, Pennsylvania; and CNRS UMR 5164, Université de Bordeaux 2, Bordeaux, France. Address reprint requests to: Zoran Ivanovic MD, PhD, Etablissement Français du Sang Aquitaine-Limousin, 5 Place Amélie Raba Léon BP 24, 33035 Bordeaux Cedex, France; e-mail: zoran.ivanovic@efs.sante.fr. This work was supported by Grant 2004.11 of Scientific Council of French Blood Establishment (Etablissement Français du Sang). Received for publication March 2, 2005; revision received May 17, 2005, and accepted May 19, 2005. doi: 10.1111/j.1537-2995.2006.00677.x TRANSFUSION 2006;46:118-125. TRANSPLANTATION AND CELLULAR ENGINEERING Whole-blood leukodepletion filters as a source of CD34 + progenitors potentially usable in cell therapy Zoran Ivanovic, Pascale Duchez, Doris A. Morgan, Francis Hermitte, Xavier Lafarge, Jean Chevaleyre, Vincent Praloran, Bernard Dazey, Gérard Vezon, and Jean-Michel Boiron BACKGROUND: Used leukodepletion filters (LDFs), containing billions of white blood cells (WBCs), are discarded. Because the steady-state blood contains low quantities of stem and progenitor cells that are retained in LDFs, the viability and the functional properties of mononuclear cells (MNCs) and CD34+ cells recovered from LDFs were investigated. STUDY DESIGN AND METHODS: WBCs were recovered from LDFs by use of a closed system. MNCs and CD34+ cells were isolated from freshly LDF- recovered WBCs or after their overnight incubation. The CD34+ cells were enumerated, as well as the number of colony-forming unit (CFU)–granulocyte-macrophage, burst-forming unit–erythroid, and CFU-Mixed. The expansion in clinical-scale volume cultures (serum-free medium plus stem cell factor, granulocyte–colony- stimulating factor, and megakaryocyte growth and development factor) was performed starting from MNCs, freshly isolated CD34+ cells, and CD34+ cells isolated after overnight incubation of WBCs. The erythroid, megakaryocytic, eosinophilic, and monocyte-myelocytic lineage differentiation of LDF-recovered CD34+ cells was challenged in liquid cultures by adding relevant cytokines. RESULTS: Nearly 450 × 10 3 viable CD34+ cells were recovered per LDF. These cells exhibit unimpaired colony- forming ability. It is possible to expand these cells ex vivo, but their response to cytokines is different compared to mobilized peripheral blood and cord blood CD34+ cells. Thus, further work is necessary to optimize their ex vivo expansion. These cells give rise to the mature cells and precursors of erythroid, megakaryocytic, eosinophilic, and monomyelocytic lineage in liquid cultures. CONCLUSION: MNCs and CD34+ cells recovered from the LDFs exhibit unimpaired functional capacities. Recent development of ex vivo technologies for expansion, retrodifferentiation, and differentiation reinforces the value in cell therapy of these LDG-recovered peripheral blood progenitor cells that are routinely discarded. he increase in the number of committed progen- itors in peripheral blood after chemotherapy or/ and cytokine mobilization attracted the atten- tion of researchers and clinicians resulting in a shift in clinical practice to the transplantation of mobi- lized peripheral blood cells. Conversely, the steady-state progenitors and stem cells were not intensively studied and are not used in clinical cell therapy today. Steady-state blood contains low quantities of stem and progenitor cells. The capacity of circulating stem cells to reconstitute hematopoiesis was documented in rats 1 even before the first publication on the existence of a pluripotent hematopoietic progenitor in syngeneic mice transplantation model. 2 Later, these findings were con- firmed in baboons 3 and humans. 4 Apart from the stem cells with the capacity of hematopoietic reconstitution in vivo, steady-state peripheral blood contains the committed 5-7 and pluripotent 8-10 progenitors. Leukodepletion of blood products is mandatory in France since 1998. Used leukodepletion filters (LDFs), containing billions of white blood cells (WBC), are dis- T