CD8-positive/T-cell receptor-negative (CD8 ؉ /TCR ؊ ) graft facilitating cells (FCs) are a novel cell population in bone marrow that potently enhance engraftment of hemopoietic stem cells (HSCs). Previously, we showed that the CD11c ؉ /B220 ؉ / CD11b ؊ plasmacytoid-precursor dendritic cell (p-preDC) FC subpopulation plays a critical but nonredundant role in facilitation. In the present study, we investigated the mechanism of FC function. We report that FCs induce antigen-specific CD4 ؉ / CD25 ؉ /FoxP3 ؉ regulatory T cells ( IntroductionRecently, a great deal of interest has focused on the therapeutic potential of cell-based therapies to induce tolerance. Of greatest interest is the subpopulation of bone marrow-derived plasmacytoidprecursor dendritic cells (p-preDCs) and the regulatory T cells (Tregs) that they induce. A major limitation to the use of p-preDCs and Tregs in vivo has been the failure to identify an approach to prevent them from losing their tolerogenic properties and becoming immunogenic after transplantation. We recently demonstrated that CD8␣-positive/T-cell receptor-negative (CD8␣ ϩ /TCR Ϫ ) graft facilitating cells (FCs) enhance the engraftment of hematopoietic stem cells (HSCs) and tolerance induction in allogeneic recipients. [1][2][3] FCs suppress graft-versus-host disease (GVHD) in vivo by producing CD4 ϩ /CD25 ϩ /FoxP3 ϩ Tregs 4 and induce Tregs in vitro in the presence of CpG. 5 The majority of CD8␣ ϩ /TCR Ϫ FCs share the B220 ϩ /CD11c ϩ /CD11b Ϫ p-preDC phenotype, and we have demonstrated the first in vivo engraftment-enhancing and tolerancepromoting effect of the p-preDC FC subpopulation. 2 Although removal of p-preDC FCs from total FCs completely abrogates facilitation, p-preDC FCs alone do not replace FCs to provide the full in vivo biologic effect of facilitation. The mechanism of FC function has yet to be precisely characterized.CD4 ϩ /CD25 ϩ /FoxP3 ϩ Tregs play a critical role in the maintenance of self-tolerance. 6 Defects in Treg development or homeostasis result in systemic autoimmunity, 7 whereas adoptive transfer of Tregs as a therapeutic method can control ongoing autoimmune diseases. [8][9][10] Recently, several studies have demonstrated an important role for Tregs in mediating transplantation tolerance in animal models, 11-14 but little is known about the mechanism of Treg development and homeostasis. [15][16][17] p-preDCs may be important in the generation of Tregs, as evidenced by their potential to facilitate engraftment of HSCs 2,18 and to prolong heart allograft survival. 19,20 In addition, in vitro activation of p-preDCs with CpGoligodeoxynucleotides (CpG-ODNs) induces the production of Tregs in vitro. 5,21 We therefore evaluated whether the mechanism of FC function in vivo is to induce Tregs.In the present study, we first evaluated whether FCs enhance allogeneic HSC engraftment in diabetes-prone nonobese diabetic (NOD) mice. Second, we investigated whether FCs induce the production of Tregs and examined their function using in vivo transplantation models and in vitr...

What's the best way to get "close to the customer"? One company has developed a customer feedback system to drive product design, sales, service, and support functions in order to ensure better customer responsiveness.

CD8 1 TCR 2 graft facilitating cells (FCs) enhance engraftment of hematopoietic stem cells (HSCs) in allogeneic and syngeneic recipients. The mechanisms by which FCs promote HSC engraftment and tolerance induction have not been fully elucidated. Here, we provide data to support a critical role for dedicator of cytokinesis 2 (DOCK2) in multiple aspects of FCs function. DOCK2 2/2 FCs exhibit compromised facilitative function in vivo as evidenced by the loss of engraftmentenhancing capability for c-Kit 1 Sca-1 1 lineage 2 (KSL) cells, and compromised ability to promote KSL cell homing and lodgment in hematopoietic niche. Deletion of DOCK2 abrogates the ability of FCs to induce differentiation of na€ ıve CD4 1 CD25 2 T cells into FoxP3 1 regulatory T cells and interleukin-10-producing type 1 regulatory T cells in vitro. Moreover, DOCK2 2/2 FCs are unable to promote survival of KSL cells when cocultured with KSL cells. DOCK2 2/2 FCs also exhibit compromised migration to stroma-derived factor-1 in vitro and impaired homing to the bone marrow in vivo. In conclusion, our results demonstrate that DOCK2 is critical for FCs to maintain its immunomodulatory function and exert its trophic effects on KSL cells. These findings may have direct clinical relevance to promote HSC engraftment for treatment of autoimmunity, hemoglobinopathies, and to induce transplantation tolerance.

No abstract

OBJECTIVE-PlasmacytoidCONCLUSIONS-These data demonstrate that NOD FCs exhibit significantly impaired function that is reversible, since FL restored production of functional FCs in NOD mice and suggest that FL plays an important role in the regulation and development of FC function. FCs may therefore be linked to diabetes pathogenesis and prevention.