Jagged2-expressing hematopoietic progenitors promote regulatory T cell expansion in the periphery through notch signaling.

Cellular interactions promoting the in vivo expansion of CD4(+)CD25(+)Foxp3(+) regulatory T (Treg) cells for maintenance of immune tolerance remain poorly defined. Here we report that mobilized Lin(-)Sca-1(+)c-kit(+) (LSK) hematopoietic progenitor cells (HPCs), unlike medullary hematopoietic stem cells (HSCs), selectively drove the direct, immediate expansion of functional host-derived Treg cells, thereby preventing the progression to overt spontaneous autoimmune diabetes in nonobese diabetic mice. Treg cell expansion required cell-to-cell contact and Notch3 signaling, which was mediated selectively through the Notch ligand Jagged2 expressed by the multipotent HPC subset, as assessed by small interfering RNA (siRNA) silencing. Conversely, notwithstanding their similar multilineage microchimerism, neither sorted Jagged2(-) HPCs nor Jagged2(lo) medullary HSCs were able to expand Treg cells. These data provide evidence for a productive Notch-mediated interaction between a unique subset of mobilized hematopoietic progenitors and Treg cells. They open therapeutic perspectives for autologous transplantation of Jagged2(+) LSK progenitors to promote Treg cell expansion in T cell-mediated diseases.

G-CSF treatment prevents cyclophosphamide acceleration of autoimmune diabetes in the NOD mouse.

Cyclophosphamide (CY) accelerates autoimmune diabetes in the NOD mouse at different levels, including critical targeting of a regulatory T cell subset, exacerbation of pro-Th1 IFN-gamma production and promotion of inflammation in pancreatic islets. Here we evaluated the ability of G-CSF to antagonize the acceleration of the disease induced by CY. Human recombinant G-CSF, administered daily at 200 microg/kg by s.c. injection, protected NOD mice from CY-accelerated onset of glycosuria and insulitis. G-CSF accelerated the recovery of the T cell compartment after the depletion of the lymphoid compartment triggered by CY injection. It selectively prevented the loss of the immunoregulatory T cells expressing the CD4(+)CD25+ phenotype that also stained CD62L+ in peripancreatic lymph nodes and promoted their expansion in the spleen. In addition to this, it abrogated the robust cytokine--particularly IFN-gamma- and chemokine burst triggered in immune cells by CY. G-CSF promoted only slight changes in the inflammatory effects of CY at the target tissue site, assessed by chemokine induction within the pancreas. Thus the immunoregulatory properties of G-CSF were critical in the early control of the accelerating effects of CY on autoimmune diabetes in the NOD mouse.

Treatment with granulocyte colony-stimulating factor prevents diabetes in NOD mice by recruiting plasmacytoid dendritic cells and functional CD4(+)CD25(+) regulatory T-cells.

Accumulating evidence that granulocyte colony-stimulating factor (G-CSF), the key hematopoietic growth factor of the myeloid lineage, not only represents a major component of the endogenous response to infections, but also affects adaptive immune responses, prompted us to investigate the therapeutic potential of G-CSF in autoimmune type 1 diabetes. Treatment with G-CSF protected NOD mice from developing spontaneous diabetes. G-CSF triggered marked recruitment of dendritic cells (DCs), particularly immature CD11c(lo)B220(+) plasmacytoid DCs, with reduced costimulatory signal expression and higher interferon-alpha but lower interleukin-12p70 release capacity than DCs in excipient-treated mice. G-CSF recipients further displayed accumulation of functional CD4(+)CD25(+) regulatory T-cells that produce transforming growth factor-beta1 (TGF-beta1) and actively suppressed diabetes transfer by diabetogenic effector cells in secondary NOD-SCID recipients. G-CSF's ability to promote key tolerogenic interactions between DCs and regulatory T-cells was demonstrated by enhanced recruitment of TGF-beta1-expressing CD4(+)CD25(+) cells after adoptive transfer of DCs isolated from G-CSF- relative to vehicle-treated mice into naive NOD recipients. The present results suggest that G-CSF, a promoter of tolerogenic DCs, may be evaluated for the treatment of human type 1 diabetes, possibly in association with direct inhibitors of T-cell activation. They also provide a rationale for a protective role of the endogenous G-CSF produced during infections in early diabetes.

The expression of hepatitis B spliced protein (HBSP) encoded by a spliced hepatitis B virus RNA is associated with viral replication and liver fibrosis.

BACKGROUND/AIMS: We have previously demonstrated the in vivo expression of a new spliced hepatitis B virus (HBV) protein (HBSP) encoded by a singly spliced pregenomic RNA. The present study was designed to evaluate the impact of HBSP expression on the clinical status and liver pathology of HBV infection. METHODS: Sera from 125 chronic HBV carriers were tested for the presence of HBSP antibodies by an indirect enzyme-linked immunosorbent assay test. The severity of liver damage was evaluated using the Knodell score. RESULTS: Anti-HBSP antibody prevalence in HBV chronic carriers was 46%. We highlighted the concomitant expression of HBSP protein and anti-HBSP antibody. An association between anti-HBSP antibody detection and serum markers of HBV replication was demonstrated. With respect to HBV-related liver disease, an association was only observed with the severity of fibrosis. Furthermore, an elevation of secreted tumor necrosis factor alpha (TNFalpha), but not of soluble TNFalpha receptor 75, was observed in anti-HBSP-antibody-positive patients. Multivariate analysis showed that anti-HBSP antibody detection was independently associated with viral replication, severity of fibrosis and elevated TNFalpha secretion. CONCLUSIONS: Our data suggest the hypothesis that HBSP might play a role in the natural history of HBV infection and may be involved in the pathogenesis and/or persistence of HBV infection.

G-CSF therapy of ongoing experimental allergic encephalomyelitis via chemokine- and cytokine-based immune deviation.

Converging evidence that G-CSF, the hemopoietic growth factor of the myeloid lineage, also exerts anti-inflammatory and pro-Th2 effects, prompted us to evaluate its direct therapeutic potential in autoimmune diseases. Here we report a novel activity of G-CSF in experimental allergic encephalomyelitis, a murine model for multiple sclerosis, driven by Th1-oriented autoaggressive cells. A short 7-day treatment with G-CSF, initiated at the onset of clinical signs, provided durable protection from experimental autoimmune encephalomyelitis. G-CSF-treated mice displayed limited demyelination, reduced recruitment of T cells to the CNS, and very discrete autoimmune inflammation, as well as barely detectable CNS mRNA levels of cytokines and chemokines. In the periphery, G-CSF treatment triggered an imbalance in the production by macrophages as well as autoreactive splenocytes of macrophage inflammatory protein-1alpha and monocyte chemoattractant protein-1, the prototypical pro-Th1 and pro-Th2 CC chemokines, respectively. This chemokine imbalance was associated with an immune deviation of the autoreactive response, with reduced IFN-gamma and increased IL-4 and TGF-beta1 levels. Moreover, G-CSF limited the production of TNF-alpha, a cytokine also associated with early CNS infiltration and neurological deficit. These findings support the potential application of G-CSF in the treatment of human autoimmune diseases such as multiple sclerosis, taking advantage of the wide clinical favorable experience with this molecule.