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Engraftment Of Subpopulation Of Genetic Cells : Case Study

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INTRODUCTION
CD8+TCR- facilitating cells (FC) derived from bone marrow (BM) enhance engraftment of purified hematopoietic stem cells (HSC) in allogeneic mouse recipients without causing graft-versus-host disease (GVHD).1 The major subpopulation of FC resembles plasmacytoid precursor dendritic cells (p-preDC) both phenotypically and functionally.2 Transplantation of FC results in increased expression of transforming growth factor-β (TGF-β) and the induction of the regulatory T cell (Treg) associated genes CTLA4, GITR, and Foxp3 in the spleen of mouse recipients.3 Furthermore, FC have been shown to induce CD4+CD25+Foxp3+ Treg as well as IL-10-producing type 1 Treg in vitro4 and in vivo.5-7 Removal of the p-preDC subpopulation from FC …show more content…

We found that Flt3-L-KO FC failed to facilitate engraftment of allogeneic HSC in ablatively conditioned mice (B6→NOD) as well as in mice conditioned nonmyeloablatively (B6→BALB/c). We further analyzed Treg in Flt3-L-KO mice. The number of Treg was significantly decreased in PB, spleen, thymus, and BM. The level of chemokine receptor CXCR3 expressed on Treg (in PB and spleen) or CCR5 expressed on Treg (in PB, spleen, or BM) from Flt3-L-KO mice was significantly decreased. In addition, Treg from the spleen of Flt3-L-KO fail to facilitate allogeneic HSC engraftment. Notably, Flt3-L treatment of Flt3-L-KO mice restored the p-preDC subpopulation in FC total, and led to expansion of Treg in PB, spleen, thymus, and BM. Flt3-L treatment also restored the function of Flt3-L-KO Treg in facilitating engraftment of allogeneic HSC. Our findings suggest that Flt3-L is an important regulator in the development and homeostasis of p-preDC FC and induction of Treg generation. MATERIALS AND METHODS Mice. Four- to six- week-old male or female C57BL/6 (B6; H-2b) mice and BALB/c (H-2d) male mice were purchased from the Jackson Laboratories. Male and female Flt3-ligand knockout (Flt3-L-KO; B6 background; H-2b) mice and female NOD (H-2 g 7) mice of the same age were purchased from Taconic Laboratories. Flt3-L-KO mice were generated as previously described.12 Animals were housed in the barrier animal facility at the Institute for Cellular

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