Decoy receptor 3 protects non-obese diabetic mice from autoimmune diabetes by regulating dendritic cell maturation and function

Decoy receptor 3 (DcR3), a member of the tumor necrosis factor receptor superfamily, regulates immune responses through competing with receptors of Fas ligand (FasL), LIGHT and TNF-like molecule 1A (TL1A). We have previously demonstrated that transgenic expression of DcR3 in a β cell-specific manner significantly protects non-obese diabetic (NOD) mice from autoimmune diabetes. In this study, we further investigated the systemic effect of DcR3 in regulating lymphocytes and dendritic cells in NOD mice. Our results demonstrated that both DcR3 plasmid and protein treatments significantly inhibited insulitis and diabetes. Lymphocytes from DcR3.Fc-treated mice revealed less proliferative potential and transferred ameliorated diabetes. By administration of DcR3.Fc in T1 and T2 double transgenic NOD mice expressing human Thy1 or murine Thy1.1 surface marker under IFN-γ or IL-4 promoter control respectively, we observed a remarkable reduction of Th1 and an increase of Th2 immune responses in vivo. Strikingly, in vitro polarization experiments exhibited that not only Th1 but also Th17 cell differentiation was significantly inhibited in splenocytes treated with DcR3.Fc protein. However, this phenomenon was only observed in splenocytes, not in purified CD4⁺ T cells, suggesting that DcR3-mediated inhibition of Th1 and Th17 differentiation is not T cell-autonomous and maybe through other cell types such as dendritic cells. Finally, our results demonstrated that DcR3 directly modulates the differentiation and maturation of dendritic cells and subsequently regulates the differentiation and effector function of T cells.     

Modulation of macrophage differentiation and activation by decoy receptor 3

Decoy receptor 3 (DcR3) is a soluble receptor of the tumor necrosis factor receptor superfamily and is readily detected in certain cancer patients. Recently, we demonstrated that DcR3.Fc-treated dendritic cells skew T cell responses to a T helper cell type 2 phenotype. In this study, we further asked its ability to modulate CD14+ monocyte differentiation into macrophages induced by macrophage-colony stimulating factor in vitro. We found that DcR3.Fc was able to modulate the expression of several macrophage markers, including CD14, CD16, CD64, and human leukocyte antigen-DR. In contrast, the expression of CD11c, CD36, CD68, and CD206 (mannose receptor) was not affected in the in vitro culture system. Moreover, phagocytic activity toward immune complexes and apoptotic bodies as well as the production of free radicals and proinflammatory cytokines in response to lipopolysaccharide were impaired in DcR3.Fc-treated monocyte-derived macrophages. This suggests that DcR3.Fc might have potent, suppressive effects to down-regulate the host-immune system.     

Disease-modifying capability of murine Flt3-ligand DCs in experimental autoimmune encephalomyelitis

Dendritic cells (DCs) bridge the innate and adaptive immune response, are uniquely capable of priming na?ve T cells, and play a critical role in the initiation and regulation of autoimmune and immune-mediated disease. At present, in vivo expansion of DC populations is accomplished primarily through the administration of the recombinant human growth factor fms-like tyrosine kinase 3 ligand (hFL), and in vitro DCs are generated using cytokine cocktails containing GM-CSF +/- IL-4. Although hFL has traditionally been used in mice, differences in amino acid sequence and biological activity exist between murine FL (mFL) and hFL, and resultant DC populations differ in phenotype and immunoregulatory functional capabilities. This study developed and characterized mFL-generated DCs and determined the therapeutic capability of mFL DCs in the autoimmune disease experimental autoimmune encephalomyelitis (EAE). Our findings demonstrate that mFL and hFL expand splenic DCs equally in vivo but that mFL-expanded, splenic DCs more closely resemble normal, resting, splenic DCs. In addition, a novel method for generating mFL-derived bone marrow-derived DCs (BM-DCs) was developed, and comparison of mFL with hFL BM-DCs found mFL BM-DCs to be less mature (i.e., lower MHC Class II, CD80, and CD86) than hFL BM-DCs. These immature mFL DCs up-regulated costimulatory molecules in response to maturation stimuli LPS and TNF-alpha. Mature mFL BM-DCs were immunogenic and exacerbated the clinical disease course of EAE.     

Effects of DKK-3, a Wnt signaling inhibitor,on dendritic cell phenotype and T cell polarization

Abstract

Wnt signaling plays crucial roles in regulation of a wide range of processes in different cell types including immune cells and, in particular, dendritic cells and T cells. Growing indications point out that Wnt pathway components modulate the both innate and adaptive immune responses through regulating DC functions. We investigated the effects of recombinant DKK-3 protein on the phenotype and biological functions of bone marrow-derived DCs (BM-DCs) as well as T cell polarization. The phenotype and the cytokine production of BM-derived DCs in the presence DKK-3 were analyzed using flow cytometry and ELISA, respectively. Also, capability of DCs to activate T cells was evaluated by CFSE-labeled splenocytes. Regulatory T cell induction, T cell polarization, and cytokine secretion were assessed by flow cytometry and ELISA in splenocytes cultured in the presence of DKK-3. Our results showed that the expression of CD86 and CD40 increased in the DKK-3-treated DC, while the expression of PDL-1 and PDL-2 diminished. Furthermore, the presence of DKK-3 decreased IL-10 and IL-4 production and increased IFN-gamma production by treated DCs.DKK-3. Moreover, DKK-3 shifted naive CD4 T cells towards T_H1 cells through up-regulation of T-bet and down-regulation of GATA-3. Our results, therefore, suggest that DKK-3 protein has the ability to promote the generation of Th1-immunostimulatory DCs from its precursors.     

Nitric oxide controls an inflammatory-like Ly6C(hi)PDCA1+ DC subset that regulates Th1 immune responses

Using NOS2 KO mice, we investigated the hypothesis that NO modulation of BM-DC contributes to the NO-mediated control of Th1 immune responses. BM-DCs from NOS2 KO mice, compared with WT BM-DCs, have enhanced survival and responsiveness to TLR agonists, develop more Ly6C(hi)PDCA1(+) DCs that resemble inflammatory DCs and produce high levels of inflammatory cytokines. Also, compared with WT-infected mice, NOS2 KO mice infected with WNV showed enhanced expansion of a similar inflammatory Ly6C(hi)PDCA1(+) DC subset. Furthermore, in contrast to WT DCs, OVA-loaded NOS2 KO BM-DCs promoted increased IFN-γ production by OTII CD4(+) T cells in vitro and when adoptively transferred in vivo. The addition of a NO donor to NOS2 KO BM-DCs prior to OTII T cells priming in vivo was sufficient to revert Th1 immune responses to levels induced by WT BM-DCs. Thus, autocrine NO effects on maturation of inflammatory DCs and on DC programming of T cells may contribute to the protective role of NO in autoimmune diseases and infections. Regulating NO levels may be a useful tool to shape beneficial immune responses for DC-based immunotherapy.     

CD40 ligation releases immature dendritic cells from the control of regulatory CD4+CD25+ T cells

We report that disruption of CD154 in nonobese diabetic (NOD) mice abrogates the helper function of CD4+CD25- T cells without impairing the regulatory activity of CD4+CD25+ T cells. Whereas CD4+ T cells from NOD mice enhanced a diabetogenic CD8+ T cell response in monoclonal TCR-transgenic NOD mice, CD4+ T cells from NOD.CD154(-/-) mice actively suppressed it. Suppression was mediated by regulatory CD4+CD25+ T cells capable of inhibiting CD8+ T cell responses induced by peptide-pulsed dendritic cells (DCs), but not peptide/MHC monomers. It involved inhibition of DC maturation, did not occur in the presence of CD154+ T-helper cells, and could be inhibited by activation of DCs with LPS, CpG DNA, or an agonistic anti-CD40 mAb. Thus, in at least some genetic backgrounds, CD154-CD40 interactions and innate stimuli release immature DCs from suppression by CD4+CD25+ T cells.     

Targeting pre-ligand assembly domain of TNFR1 ameliorates autoimmune diseases - an unrevealed role in downregulation of Th17 cells

The pre-ligand assembly domain (PLAD) of tumor necrosis factor receptors mediates specific ligand-independent receptor assembly and subsequent signaling. However, the physiological role of PLAD in the regulation of TNFR-mediated immune responses in autoimmunity is still unclear. By using the recombinant PLAD.Fc protein to block TNFR1 assembly, we demonstrated that PLAD.Fc treatment significantly reduced the TNFR1-driving proinflammatory cytokines and protected NOD mice from diabetes. Strikingly, Th17 differentiation was significantly inhibited in PLAD.Fc-treated NOD and TNFR1-deficient mice, indicating a TNFR1-dependent Th17 development. PLAD.Fc-modulated effects on DCs, in terms of the downregulation of Th17-inducing cytokines, IL-6 and TGF-β, explained the potential mechanism for Th17 suppression. Finally, we provided an additional result that PLAD.Fc administration diminished the infiltration of Th17 cells in the central nervous system and ameliorated the experimental autoimmune encephalomyelitis in mice. Collectively, these data demonstrated that targeting PLAD of TNFR1 provides protection from autoimmune diseases through the downregulation of Th17 and suggested a therapeutic potential of PLAD-modulation in TNF-involved inflammatory diseases.     

Complement C5a anaphylatoxin is an innate determinant of dendritic cell-induced Th1 immunity to Mycobacterium bovis BCG infection in mice

During acquired immunity to Mycobacterium bovis bacillus Calmette-Guerin (BCG) infection in mice, dendritic cells (DCs) present mycobacterial antigens to naive T cells to prime an immune response. Complement C5a (anaphylatoxin) secreted by mycobacteria-infected macrophages regulates IL-12p70 production. As IL-12p70 regulates Th1 immunity against mycobacteria in mice, we examined the effects of C5a on IL-12p70 secretion by murine DCs and Th1 immunity. DCs cultured from C5-deficient (C5(-/-)) and -sufficient (C5(+/+)) mice were infected with BCG in the presence or absence of the C5a peptide. ELISA showed that C5(-/-) DCs secreted less IL-12p70 (600 pg/mL vs. 100 pg/mL) than C5(+/+) DCs, and they secreted more IL-10. Using immunophenotyping, reduced CD40 expression was found on C5(-/-) DCs after BCG infection. BCG-primed DCs were then cocultured with naive or BCG-immune T cells to differentiate them into IFN-gamma-secreting Th1 T cells. Coincident with increased IL-12p70 levels, BCG-primed C5(+/+) DCs cocultured with naive or immune C5(+/+) T cells showed a larger increase in CD4+ IFN-gamma/CD8+ IFN-gamma+ T cells compared with cocultured DCs and T cells from C5(-/-) mice. Thus, BCG-primed C5(+/+) DCs were better able to drive a Th1 response. Furthermore, BCG aerosol-infected C5(-/-) mice showed reduced CD4 and CD8 IFN-gamma-secreting T cells in the lungs, concurrent with an increased growth of BCG. Thus, C5a, an innate peptide, appears to play an important role in the generation of acquired immune responses in mice by regulating the Th1 response through modulation of IL-12p70 secretion from DCs.     

Role of aquaporin 3 in development, subtypes and activation of dendritic cells

Dendritic cells (DCs) uptake soluble antigens and large volumes of fluid through macropinocytosis and migrate for antigen presentation. Aquaporin 3 (AQP3), a water and glycerol transporting protein, is highly expressed in immature DCs. To elucidate the role of AQP3 in DC function, we investigated subtype and activation of DCs in AQP3 knock-out (AQP3(-/-)) mice. Depletion of AQP3 did not affect the development of bone marrow-derived DCs (BM-DCs) by GM-CSF or the Flt3 ligand and the level of expression of CD86 on unstimulated and LPS-stimulated BM-DCs. In addition, the percentage of CD86(+) cells among splenic cDCs after LPS treatment in both in vitro and in vivo conditions was similar in wild type and AQP3(-/-) mice. However, the frequency of CD4(+) cDCs in the spleen of AQP3(-/-) mice was significantly lower than that of wild type mice. There was higher expression of CD103 in the CD8(+) subpopulation of splenic cDCs from AQP3(-/-) mice than wild type mice. In the dermis, more CD103-expressing cells were detected in AQP3(-/-) mice than in wild type mice and the LPS-induced decrease of CD103(+) dermal DCs was impaired in AQP3(-/-) mice. AQP3 depletion did not affect the uptake of either albumin or dextran by CD11c(+) splenic DCs. However, HgCl(2), which is an AQP inhibitor, significantly inhibited the uptake of albumin but not dextran by CD11c(+) splenic DCs. These results suggest that AQP3 may play a role in modulating DC population and migration.     

MHC class I-mediated exogenous antigen presentation by exosomes secreted from immature and mature bone marrow derived dendritic cells

Exosomes are 50-90 nm vesicles with antigen presenting ability carrying major histocompatibility complex (MHC) class I, class II, abundant co-stimulatory molecules and some tetraspan proteins. Although dendritic cells (DCs) are one of the professional antigen presenting cells capable of presenting exogenous antigens in MHC class I-mediated antigen specific manner (cross-presentation), the cross-presentation ability by exosomes from immature or mature DCs are unknown. Here we show that exosomes released from ovalbumin (OVA) protein-pulsed bone marrow derived dendritic cells (BM-DCs) weakly present the peptide determinants to OVA specific MHC class I-restricted CD8(+) T cell hybridomas. The exosomes secreted by OVA(257-264) peptide- or OVA protein-pulsed mature BM-DCs activated OVA specific MHC class I-restricted T cell hybridomas more efficiently than those from immature BM-DCs. Transporters associated with antigen processing (TAP) deficient mice-derived BM-DCs were also used to examine whether functional TAP activity was required for cross-presentation by exosomes. The exosomes obtained from OVA(257-264) peptide-pulsed BM-DCs derived from TAP(-/-) mice showed a significant antigen presenting ability to OVA specific MHC class I-restricted T cell hybridomas. Altogether, our data indicate that BM-DCs secrete exosomes with weak cross-presentation ability.     

Analysis of the maturation process of dendritic cells deficient for TNF and lymphotoxin-alpha reveals an essential role for TNF

Dendritic cells (DCs) generated from bone marrow (BM) precursor cells of C57BL/6 (B6.WT) mice and cultured in the presence of granulocyte macrophage-colony stimulating factor differentiate to mature BM-DCs spontaneously. These mature DCs are characterized by high levels of major histocompatibility complex (MHC) class II, CD40, and CD86 on their surface. To analyze the involvement of tumor necrosis factor (TNF) and the related cytokine lymphotoxin (LT)alpha in DC maturation, we studied the development of DCs from the BM of B6.TNF(-/-), B6.LTalpha(-/-), and B6.TNF/LTalpha(-/-) mice and compared it to B6.WT mice. Although the development of BM precursor cells to the level of immature DCs (CD11c(+), MHC class II(low), CD40(low), and CD86(low)) was equivalent in all genotypes, B6.TNF(-/-) and B6.TNF/LTalpha(-/-) cells showed an impaired capacity to differentiate to mature DCs. In contrast, mature BM-DCs generated from LTalpha-negative, immature DCs developed like B6.WT cells. Further studies revealed that once matured, the phenotype of all tested genotypes was comparable. They expressed high levels of CD40 and CD86, were exclusively positive for the chemokine receptor (CCR)7 but negative for CCR5 and CCR2, and were able to enter the paracortex of draining lymph nodes. The limited maturation of TNF-deficient BM-DCs could be restored by mixing TNF-negative with TNF-positive Ly5.1 BM cells, and maturation of B6.WT DCs could be blocked with an anti-TNF monoclonal antibody. The substitution of B6.TNF(-/-) BM cells with recombinant TNF revealed promotion or suppression of BM-DC maturation depending on the point of time of TNF addition.     

Aqueous extract of Phyllanthus niruri (Euphorbiaceae) enhances the phenotypic and functional maturation of bone marrow-derived dendritic cells and their antigen-presentation function

Decoctions of Phyllanthus niruri (PN) (Fam. Euphorbiaceae) is promoted in traditional medicine of Africa, Asia, and South America as beneficial supplement for different infectious diseases, especially for viral hepatitis, tumor, and for immune compromised patients. This stimulated the interest in understanding the mechanisms by which the whole extract of the plant could stimulate the immune system. Dendritic cells (DCs) are professional antigen-presenting cells and provide a link between the innate and the adaptive immune responses. In the present study, the effects of lyophilized aqueous extract of PN on structural and functional maturation of murine bone marrow-derived DCs (BM-DCs) were investigated. Bone marrow cells were cultured in the presence of granulocyte macrophage–colony stimulating factor and interleukin-4 (IL-4) and the generated immature DCs were stimulated with PN (25, 50, and 100 μg/mL) or lipopolysaccharide (10 μg/mL) for 48?h. Results showed that treatment with PN increased the expression of major histocompatibility complex-II and the various makers for DCs maturation (CD40), activation (CD83), and costimulation (CD86) in a concentration-dependent manner. Consistent with the increase in phenotypic makers, functional maturation assay showed that treatment of BM-DCs with PN caused a decrease in fluorescein isothiocyanate-dextran pinocytosis and an increase in IL-12 in the supernatant. In a transgenic T-cell activation model, PN-treated BM-DCs presented Ova antigen to Ova-specific CD8⁺ T cells from OT-1 mice more efficiently as demonstrated by increased T-cells proliferation and IL-2 production. Therefore, PN enhances the structural and functional maturation of BM-DCs and their antigen-presenting function. These effects are relevant in immunodeficient conditions, tumor control, and in infectious diseases.     

Apoptosis resistance in ulcerative colitis: high expression of decoy receptors by lamina propria T cells

Intestinal mucosa is constantly exposed to normal environmental antigens. A significant number of intestinal mucosal T cells are being deleted through apoptosis. In contrast, T cells from inflamed mucosa of ulcerative colitis patients did not undergo apoptosis. In this study, we determined whether the apoptosis of normal mucosal T cells was induced by antigen receptor stimulation and further determined pathways that mediated the apoptosis. Freshly isolated lamina propria T cells were stimulated with CD3 mAb and apoptosis was determined by Annexin V staining. Normal mucosal T cells underwent apoptosis upon CD3 mAb stimulation whereas the T cells from inflamed mucosa did not. The apoptosis in normal T cells was blocked by TRAIL-R1:Fc and an inhibiting CD95 antibody. Interestingly, decoy receptor (DcR)1, DcR2, and DcR3 that compete with death receptor (DR)4/5 and CD95 were highly expressed by the T cells from inflamed mucosa, but much lower by T cells from normal mucosa. Our data suggest that normal mucosal T cells are constantly deleted in response to environmental antigens mediated through DR4/5 and CD95 pathways and mucosal T cells from ulcerative colitis resist to undergoing apoptosis due to highly expression of DcR1, DcR2, and DcR3.     

Analysis of the CCR7 expression on murine bone marrow-derived and spleen dendritic cells

About 40% of bone marrow-derived dendritic cells (BM-DCs) generated from stem cells of C57BL/6 (B6.WT) mice differentiate in the presence of granulocyte macrophage-colony stimulating factor (GM-CSF) without further stimuli to mature DCs. These cells are characterized by high levels of major histocompatibility complex class II, CD40, and CD86 on their surface. Recent studies have revealed that tumor necrosis factor (TNF) is crucial for maturation of BM-DCs. However, once matured, the phenotype of mature TNF-negative C57BL/6 (B6.TNF-/-) and B6.WT BM-DCs is comparable. Both expressed high levels of CD40 and CD86 and were positive for mRNA of the chemokine receptor (CCR)7. To extend our studies, we generated a monoclonal antibody (mAb) specific for mouse CCR7. This mAb allowed us to analyze the surface expression of CCR7 during maturation of B6.WT and B6.TNF-/- BM-DCs in the presence of GM-CSF and stimulated with TNF or lipopolysaccharide (LPS) and to compare it with the CCR7 expression on ex vivo-isolated splenic DCs with or without additional stimulation. Our results showed that CCR7 expression on murine BM-DCs is an indication of cell maturity. Incubation with LPS induced the maturation of all BM-DCs in culture but increased the number of mature CCR7+ splenic DCs only marginally.     

Immune tolerance induced by intravenous transfer of immature dendritic cells via up-regulating numbers of suppressive IL-10+ IFN-γ+-producing CD4+ T cells

Dendritic cells (DCs) regulate immunity and immune tolerance in vivo. However, the mechanisms of DC-mediated tolerance have not been fully elucidated. Here, we demonstrate that intravenous (i.v.) transfer of bone marrow-derived DCs pulsed with myelin oligodendrocyte glycoprotein (MOG) peptide blocks the development of experimental autoimmune encephalomyelitis in C57BL/6J mice. i.v. transfer of MOG-pulsed DCs leads to the down-regulation of the production of IL-17A and IFN-γ and up-regulation of IL-10 secretion. The development of regulatory T cells (Tregs) is facilitated via up-regulation of FoxP3 expression and production of IL-10. The number of suppressive CD4⁺IL-10⁺IFN-γ⁺ T cells is also improved. The expression of OX40, CD154, and CD28 is down-regulated, but the expression of CD152, CD80, PD-1, ICOS, and BTLA is up-regulated on CD4⁺ T cells after i.v. transfer of immature DCs. The expression of CCR4, CCR5, and CCR7 on CD4⁺ T cells is also improved. Our results suggest that immature DCs may induce tolerance via facilitating the development of CD4⁺FoxP3⁺ Tregs and suppressive CD4⁺IL-10⁺IFN-γ⁺ T cells in vivo.     

The glucocorticoid-induced tumor necrosis factor receptor-related gene modulates the response to Candida albicans infection

The glucocorticoid-induced tumor necrosis factor (TNF) receptor-related gene (GITR; TNFRSF18) modulates immune response activating coaccessory signals in T cells and is expressed at high levels in CD4+CD25+ cells. Its ligand (GITRL) is expressed in antigen-presenting cells, where it is capable of promoting signaling. We investigated the role of GITR/GITRL interaction during disseminated candidiasis in GITR knockout (GITR-/-) mice. GITR-/- mice survived longer and had a significantly decreased yeast load in kidneys and brain compared to GITR+/+ mice. Since protective immunity to the fungus is mediated by antigen-specific T helper (Th) 1 cells, we studied in vitro cytokine production following infection. CD4+ T cells of GITR-/- mice demonstrated a more efficient Th1 polarization as suggested by a two- to threefold decreased production of interleukin- (IL-)4 and IL-10 and a four- to fivefold increased production of gamma interferon compared to GITR+/+ mice. This effect was not due to differences in lymphocyte and dendritic cell (DC) subpopulations in infected mice as demonstrated by flow cytometric studies. To verify whether DC activity was differently modulated, DCs were cocultured with CD4+ T cells in the presence of heat-inactivated Candida albicans. DCs, cocultured with GITR+/+ CD4+CD25+ cells produced a lower amount of IL-12 than DCs cocultured with GITR-/- CD4+CD25+ T cells. These results suggest that GITR regulates susceptibility to systemic candidiasis by negatively modulating IL-12 production and promoting polarization of CD4+ T cells towards Th2 by analogy with OX40, another TNF receptor superfamily member.     

Nucleotide binding oligomerization domain 2 deficiency leads to dysregulated TLR2 signaling and induction of antigen-specific colitis

In this study, we determined conditions leading to the development of colitis in mice with nucleotide binding oligomerization domain 2 (NOD2) deficiency, a susceptibility factor in Crohn's disease. We found that NOD2-deficient antigen-presenting cells (APCs) produced increased amounts of interleukin (IL)-12 in the presence of ovalbumin (OVA) peptide and peptidoglycan or recombinant E. coli that express OVA peptide (ECOVA). Furthermore, these APCs elicited heightened interferon-gamma (IFN-gamma) responses from cocultured OVA-specific CD4+ T cells. We then demonstrated that NOD2-deficient mice adoptively transferred OVA-specific CD4+ T cells and that administered intrarectal ECOVA developed colitis associated with the expansion of OVA-specific CD4+ T cells producing IFN-gamma. Importantly, this colitis was highly dependent on Toll-like receptor 2 (TLR2) function since it was suppressed in NOD2 and TLR2 double-deficient mice. Thus, NOD2-deficient mice become susceptible to colitis as a result of increased TLR2 responses when they have the capacity to respond to an antigen expressed by mucosal bacteria.     

Modulation of dendritic cells using granulocyte-macrophage colony-stimulating factor (GM-CSF) delays type 1 diabetes by enhancing CD4+CD25+ regulatory T cell function

Abnormalities in DC function are implicated in defective immune regulation that leads to type-1 diabetes (T1D) in NOD mice and humans. In this study, we used GM-CSF and Flt3-L to modulate DC function in NOD mice and observed the effects on T1D development. Treatment with either ligand at earlier stages of insulitis suppressed the development of T1D. Unlike Flt3-L, GM-CSF was more effective in suppressing T1D, even when administered at later stages of insulitis. In vitro studies and in vivo adoptive transfer experiments revealed that CD4+CD25+ T cells from GM-CSF-treated mice could suppress effector T cell response and T1D. This suppression is likely mediated through enhanced IL-10 and TGF-β1 production. Adoptive transfer of GM-CSF exposed DCs to naive mice resulted in an expansion of Foxp3+ T cells and a significant delay in T1D onset. Our results indicate that GM-CSF acted primarily on DCs and caused an expansion of Foxp3+ Tregs which delayed the onset of T1D in NOD mice.     

The secretions products from invading cercariae of S. japonicum (0-3hRP) restrain mouse dendritic cells to mature

Schistosomiasis is a water-borne infection caused mainly by human schistosomes including Schistosoma mansoni (S. mansoni) and Schistosoma japonicum (S. japonicum). In the infected host, immune events in the skin appear to have an important initiating role in determining the type, and guiding the magnitude, of the ensuing acquired immune response. The previous studies of S. mansoni showed that dendritic cells (DCs) prime Th2 response after activating with products released by schistosome larvae (material released in the first 3 h after transformation, 0–3hRP). Therefore, it is interesting to know whether 0–3hRP from S. japonicum also activate DC and induce Th2 immune response. Here, we report 0–3hRP of S. japonicum failed to stimulate the maturation of bone marrow-derived DCs (BM-DCs), while soluble antigen of the body of cercariae preparation (SCAP) induced BM-DCs to mature which can be weakened by 0–3hRP. Moreover, using an in vitro ovalbumin peptide-restricted priming assay, DCs treated with 0–3hRP failed to induce T cells to secrete more cytokines than the negative control group by CD4⁺ T cells from DO11.10 transgenic mice, while DCs treated with SCAP upregulated secretions of IFN-γ and IL-17A, but downregulated IL-4. Importantly, BM-DCs treated with 0–3hRP plus SCAP induced BM-DCs selective mature which drive Th2-type polarized response. Our in vitro results agree with the findings of in vivo studies by inoculation of DO11.10 mice with different stimulus-activated DCs pulsed with ovalbumin peptide. Our data demonstrate that the secretions from invading cercariae of S. japonicum (0–3hRP) impaired DCs to mature, which is potentially allowing the parasite to negotiate the immune recognition and attack.     

CD200 Immunoadhesin Suppresses Collagen-Induced Arthritis in Mice

DBA/1 mice immunized with 100 microg bovine collagen type II emulsified in Freund's adjuvant, followed by booster injection in incomplete adjuvant at 18 days, develop profound arthritis (>50% of animals) by 30 days postinjection. The molecule CD200 (previously called OX2), associated with, among others, follicular dendritic cells, is implicated in delivery of immunosuppressive signals to the immune system, and an immunoadhesin in which the extracellular domains of CD200 were linked to a mouse IgG2a Fc region has been shown to promote renal allograft survival. DBA/1 mice receiving 15 microg/mouse CD200Fc at 3-day intervals following immunization with collagen did not develop arthritis in this model. Lymphocytes taken from CD200Fc-treated, collagen-immunized mice produced significantly lower levels of TNFalpha and IFN-gamma in culture supernatants after restimulation in vitro with collagen, in contrast to cells taken from control mice treated with PBS or normal mouse Ig. Serum from CD200Fc-treated mice contained less anti-collagen IgG (approximately 50% reduction), with relatively more IgG2b and IgG3, and lower levels of TNFalpha and IFN-gamma, than control mice. These data indicate that this immunoadhesin may have a potent role to play in the regulation of autoimmune disorders.