IntroductionMyeloid dendritic cells (DCs) are crucial antigen-presenting cells (APCs) for primary T-cell responses. They arise from bone marrow (BM) precursors that colonize peripheral tissues through the blood or lymph. 1,2 Tissue-resident immature DCs are excellent at internalizing and processing antigen, but they exhibit low ability to stimulate naive T cells. Exposure to allergens, bacterial (lipopolysaccharide [LPS], CpG DNA motifs) or viral (dsRNA) components, proinflammatory cytokines (interleukin-1␤ , tumor necrosis factor-␣ [TNF-␣], interferon ␣ [IFN-␣], granulocytemacrophage colony-stimulating factor (GM-CSF), and cognate T-cell interactions are some of the stimuli that trigger DC differentiation. 1,2 The capacity of mature DCs to prime naive T lymphocytes and to promote their differentiation into different T-cell subsets is attributed to the up-regulation of surface major histocompatibility complex (MHC), costimulatory and adhesion molecules, and the ability to secrete IL-1, Although the capacity of DCs to produce an ample repertoire of cytokines is documented in humans and rodents, there is little information on how cytokine genes are expressed during DC ontogeny. 4 In this study, we analyzed a range of cytokine transcripts and their respective proteins in highly purified mouse BM-derived myeloid DCs (BM DCs) at different stages of cell differentiation. Immature BM DCs expressed higher levels of IL-1␣, IL-1␤, TNF-␣, transforming growth factor ␤1 (TGF-␤1), and macrophage migration inhibitory factor (MIF) transcripts/ protein. After spontaneous differentiation in culture, the DCs up-regulated the levels of IL-6 and IL-15 mRNA and transcribed mRNA for IL-12p35, IL-12p40, and IL-18 de novo. Similar findings were found at the protein level by flow cytometry or enzyme-linked immunoabsorbent assay (ELISA).We also investigated the changes in the cytokine repertoire of BM DCs terminally differentiated with LPS or after CD40 cross-linking. Both stimuli increased the levels of IL-6, IL12p40, IL-15, and TNF-␣ transcripts/intracellular protein. However, only LPS markedly up-regulated the transcription of IL-1␣, IL-1␤, IL-12p35, and MIF genes. Although LPS or CD40 ligation augmented the T-cell allostimulatory capacity of DC, only LPS shifted the balance of naive T helper (Th) from a mixed Th1/Th2 population to Th1 cells, a result that agrees with the fact that only LPS was able to up-regulate the transcription of IL-12p35 in BM DCs. These results also demonstrate that, depending on the stimuli that induce the terminal differentiation of DCs, their T-cell stimulatory activity (signal 2) can be dissociated from their Th cell-driving ability (signal 3). 28 It appears that one of the key factors that regulates the Th cell-driving ability of myeloid DCs is the ability of the Materials and methods Experimental animalsTen-to 12-week-old C57BL/10 (B10; H2K b , IA b , IE Ϫ ) and C3H/He (C3H; H2K k , IA k , IE k ) mice were purchased from The Jackson Laboratory (Bar Harbor, ME) and maintained in the pathogen-free Central...

In this study, we propagated myeloid dendritic cells (DC) from BALB/c (H2d) mouse bone marrow progenitors in IL-10 and TGF-β, then stimulated the cells with LPS. These “alternatively activated” (AA) DC expressed lower TLR4 transcripts than LPS-stimulated control DC and were resistant to maturation. They expressed comparatively low levels of surface MHC class II, CD40, CD80, CD86, and programmed death-ligand 2 (B7-DC; CD273), whereas programmed death-ligand 1 (B7-H1; CD274) and inducible costimulatory ligand expression were unaffected. AADC secreted much higher levels of IL-10, but lower levels of IL-12p70 compared with activated control DC. Their poor allogeneic (C57BL/10; B10) T cell stimulatory activity and ability to induce alloantigen-specific, hyporesponsive T cell proliferation was not associated with enhanced T cell apoptosis. Increased IL-10 production was induced in the alloreactive T cell population, wherein CD4+Foxp3+ cells were expanded. The AADC-expanded allogeneic CD4+CD25+ T cells showed enhanced suppressive activity for T cell proliferative responses compared with freshly isolated T regulatory cells. In vivo migration of AADC to secondary lymphoid tissue was not impaired. A single infusion of BALB/c AADC to quiescent B10 recipients induced alloantigen-specific hyporesponsive T cell proliferation and prolonged subsequent heart graft survival. This effect was potentiated markedly by CTLA4-Ig, administered 1 day after the AADC. Transfer of CD4+ T cells from recipients of long-surviving grafts (>100 days) that were infiltrated with CD4+Foxp3+ cells, prolonged the survival of donor-strain hearts in naive recipients. These data enhance insight into the regulatory properties of AADC and demonstrate their therapeutic potential in vascularized organ transplantation.

on lymphocytes, thereby inhibiting their egress from lymphoid organs and their recirculation to inflammatory sites. Potential effects on dendritic cell (DC) trafficking have not been evaluated. Here, we demonstrate the expression of all five S1PR subtypes (S1PR1-5) by murine DCs. Administration of FTY720 to C57BL/10 mice markedly reduced circulating T and B lymphocytes within 24 h, but not blood-borne DCs, which were enhanced significantly for up to 96 h, while DCs in lymph nodes and spleen were reduced. Numbers of adoptively transferred, fluorochrome-labeled syngeneic or allogeneic DCs in blood were increased significantly in FTY720-treated animals, while donorderived DCs and allostimulatory activity for host naïve T cells within the spleen were reduced. Administration of the selective S1PR1 agonist SEW2871 significantly enhanced circulating DC numbers. Flow analysis revealed that CD11b, CD31/PECAM-1, CD54/ICAM-1 and CCR7 expression on blood-borne DCs was downregulated following FTY720 administration. Transendothelial migration of FTY720-P-treated immature DCs to the CCR7 ligand CCL19 was reduced. These novel data suggest that modulation of DC trafficking by FTY720 may contribute to its immunosuppressive effects.

Hematopoietin-mobilized renal DC are functionally immature and exhibit tolerogenic potential. Mobilization of DC within kidneys is likely to affect their antigen-handling capacity, immunogenicity, and tolerogenic ability.