C5a receptor signalling in dendritic cells controls the development of maladaptive Th2 and Th17 immunity in experimental allergic asthma

The pathways underlying dendritic cell (DC) activation in allergic asthma are incompletely understood. Here we demonstrate that adoptive transfer of ovalbumin-pulsed wild-type (wt) but not of C5a receptor-deficient (C5aR^−/−) bone marrow (BM)-derived DCs (BMDCs) induced mixed T helper type 2 (Th2)/Th17 maladaptive immunity, associated with severe airway hyperresponsiveness, mucus production, and mixed eosinophilic/neutrophilic inflammation. Mechanistically, antigen uptake, processing, and CD11b expression were reduced in C5aR^−/− BMDCs. Further, interleukin (IL)-1β, -6, and -23 production were impaired resulting in reduced Th17 cell differentiation, associated with accelerated activated T-cell death in vitro and in vivo. Surprisingly, we found an increased frequency of CD11b^hiCD11c^intGr1⁺F4/80⁺ cells, expressing arginase and nitric oxide synthase in C5aR^−/− BM preparations. Intratracheal administration of ovalbumin-pulsed wt DCs and sorted CD11b^hiCD11c^intGr1⁺F4/80⁺ C5aR^−/− cells reduced Th2 immune responses in vivo. Together, we uncover novel roles for C5aR in Th17 differentiation, T-cell survival, and differentiation of a DC-suppressor population controlling Th2 immunity in experimental allergic asthma.     

Salmonella enterica Serovar Typhimurium Infection-Induced CD11b+ Gr1+ Cells Ameliorate Allergic Airway Inflammation

Allergies are mainly characterized as an unrestrained Th2-biased immune response. Epidemiological data associate protection from allergic diseases with the exposure to certain infectious agents during early stages of life. Modulation of the immune response by pathogens has been considered to be a major factor influencing this protection. Recent evidence indicates that immunoregulatory mechanisms induced upon infection ameliorate allergic disorders. A longitudinal study has demonstrated reduced frequency and incidence of asthma in children who reported a prior infection with Salmonella. Experimental studies involving Salmonella enterica serovar Typhimurium-infected murine models have confirmed protection from induced allergic airway inflammation; however, the underlying cause leading to this amelioration remains incompletely defined. In this study, we aimed to delineate the regulatory function of Salmonella Typhimurium infection in the amelioration of allergic airway inflammation in mice. We observed a significant increase in CD11b⁺ Gr1⁺ myeloid cell populations in mice after infection with S. Typhimurium. Using in vitro and in vivo studies, we confirmed that these myeloid cells reduce airway inflammation by influencing Th2 cells. Further characterization showed that the CD11b⁺ Gr1⁺ myeloid cells exhibited their inhibitory effect by altering GATA-3 expression and interleukin-4 (IL-4) production by Th2 cells. These results indicate that the expansion of myeloid cells upon S. Typhimurium infection could potentially play a significant role in curtailing allergic airway inflammation. These findings signify the contribution of myeloid cells in preventing Th2-mediated diseases and suggest their possible application as therapeutics.     

Primary Heligmosomoides polygyrus bakeri infection induces myeloid-derived suppressor cells that suppress CD4+ Th2 responses and promote chronic infection

Primary infection with the gastrointestinal nematode Heligmosomoides polygyrus bakeri is chronic in C57BL/6 (B6) mice whereas challenge infection is rapidly eliminated. F4/80⁻CD11b⁺Gr⁺ cells, presumed to be neutrophils, were reported to accumulate around encysting larvae in intestinal tissue during primary infection, but their exact identity and role remain unclear. We observed significant increases in F4/80⁻CD11b^hiGr1^hi cells in mesenteric lymph nodes (MLNs) and spleen after primary but not challenge infection; a high proportion of these cells expressed Ly6G and Ly6C. These cells, which phenotypically resemble myeloid-derived suppressor cells (MDSC), increased in lamina propria (LP) early during primary infection. Increased MDSC were associated with low numbers of alternatively activated macrophages (AAMØ) in LP and CD4⁺GATA3⁺ T cells and AAMØ in MLN and spleen. Purified CD11c⁻CD11b⁺Gr1⁺ cells from H. polygyrus bakeri-infected mice suppressed OVA-specific CD4⁺ T-cell proliferation via a nitric oxide-dependent mechanism and parasite-specific IL-4 secretion in vitro. Adoptive transfer of CD11c⁻CD11b⁺Gr1⁺ cells from mice with primary infection resulted in significantly higher adult worm burdens and increased egg production in naïve B6 recipients infected with H. polygyrus bakeri. Altogether, these findings indicate that primary H. polygyrus bakeri infection induces a novel subset of MDSC that suppress CD4⁺ Th2 responses and promote chronic infection.     

Hierarchy of immunosuppressive strength among myeloid‐derived suppressor cell subsets is determined by GM‐CSF

CD11b⁺/Gr‐1⁺ myeloid‐derived suppressor cells (MDSC) contribute to tumor immune evasion by restraining the activity of CD8⁺ T‐cells. Two major MDSC subsets were recently shown to play an equal role in MDSC‐induced immune dysfunctions: monocytic‐ and granulocytic‐like. We isolated three fractions of MDSC, i.e. CD11b⁺/Gr‐1^high, CD11b⁺/Gr‐1^int, and CD11b⁺/Gr‐1^low populations that were characterized morphologically, phenotypically and functionally in different tumor models. In vitro assays showed that CD11b⁺/Gr‐1^int cell subset, mainly comprising monocytes and myeloid precursors, was always capable to suppress CD8⁺ T‐cell activation, while CD11b⁺/Gr‐1^high cells, mostly granulocytes, exerted appreciable suppression only in some tumor models and when present in high numbers. The CD11b⁺/Gr‐1^int but not CD11b⁺/Gr‐1^high cells were also immunosuppressive in vivo following adoptive transfer. CD11b⁺/Gr‐1^low cells retained the immunosuppressive potential in most tumor models. Gene silencing experiments indicated that GM‐CSF was necessary to induce preferential expansion of both CD11b⁺/Gr‐1^int and CD11b⁺/Gr‐1^low subsets in the spleen of tumor‐bearing mice and mediate tumor‐induced tolerance whereas G‐CSF, which preferentially expanded CD11b⁺/Gr‐1^high cells, did not create such immunosuppressive environment. GM‐CSF also acted on granulocyte–macrophage progenitors in the bone marrow inducing local expansion of CD11b⁺/Gr‐1^low cells. These data unveil a hierarchy of immunoregulatory activity among MDSC subsets that is controlled by tumor‐released GM‐CSF.     

Macrophages are critical to the maintenance of IL-13-dependent lung inflammation and fibrosis

The roles of macrophages in type 2-driven inflammation and fibrosis remain unclear. Here, using CD11b-diphtheria toxin receptor (DTR) transgenic mice and three models of interleukin 13 (IL-13)-dependent inflammation, fibrosis, and immunity, we show that CD11b⁺ F4/80⁺ Ly6C⁺ macrophages are required for the maintenance of type 2 immunity within affected tissues but not secondary lymphoid organs. Direct depletion of macrophages during the maintenance or resolution phases of secondary Schistosoma mansoni egg-induced granuloma formation caused a profound decrease in inflammation, fibrosis, and type 2 gene expression. Additional studies with CD11c-DTR and CD11b/CD11c-DTR double-transgenic mice suggested that macrophages but not dendritic cells were critical. Mechanistically, macrophage depletion impaired effector CD4⁺ T helper type 2 (Th2) cell homing and activation within the inflamed lung. Depletion of CD11b⁺ F4/80⁺ Ly6C⁺ macrophages similarly reduced house dust mite-induced allergic lung inflammation and suppressed IL-13-dependent immunity to the nematode parasite Nippostrongylus brasiliensis. Consequently, therapeutic strategies targeting macrophages offer a novel approach to ameliorate established type 2 inflammatory diseases.     

UV inhibits allergic airways disease in mice by reducing effector CD4+ T cells

Background In human asthma, and experimental allergic airways disease in mice, antigen‐presenting cells and CD4⁺ effector cells at the airway mucosa orchestrate, and CD4⁺CD25⁺ regulatory T cells attenuate, allergen immunity. UV irradiation of skin before sensitization with ovalbumin (OVA) causes significantly reduced asthma‐like responses in respiratory tissues. Objective To determine whether UV‐induced changes in CD11c⁺ cells, CD4⁺CD25⁺ effector cells or CD4⁺CD25⁺ regulatory cells in the trachea and airway draining lymph nodes (ADLNs) were responsible for reduced allergic airways disease. Methods The phenotype and function of CD11c⁺ cells and CD4⁺CD25⁺ cells in the trachea and ADLNs of UV‐ and non‐irradiated, OVA‐sensitized mice was examined 24 h after a single exposure to aerosolized OVA. Results No changes in the function of CD11c⁺ cells from UV‐irradiated mice were observed. CD4⁺CD25⁺ cells from UV‐irradiated, OVA‐sensitized mice harvested 24 h after OVA aerosol proliferated less in response to OVA in vitro and were unable to suppress the proliferation of OVA‐sensitized responder cells. This result suggested reduced activation of effector T cells in the airway mucosa of UV‐irradiated, OVA‐sensitized mice. To exclude regulatory cells of any type, there was similar proliferation in vivo to aerosolized OVA by CFSE‐loaded, OVA‐TCR‐specific CD4⁺ cells adoptively transferred into UV‐ and non‐irradiated, OVA‐sensitized mice. In addition, there was no difference in the expression of regulatory T cell markers (Foxp3, IL‐10, TGF‐β mRNA). To examine effector T cells, ADLN cells from UV‐irradiated, OVA‐sensitized and ‐challenged mice were cultured with OVA. There was reduced expression of the early activation marker CD69 by CD4⁺CD25⁺ cells, and reduced proliferation in the absence of the regulatory cytokine, IL‐10. Conclusion Reduced allergic airways disease in UV‐irradiated mice is due to fewer effector CD4⁺CD25⁺ cells in the trachea and ADLNs, and not due to UV‐induced regulatory cells. Cite this as: J. P. McGlade, D. H. Strickland, M. J. M. Lambert, S. Gorman, J. A. Thomas, M. A. Judge, J. T. Burchell, G. R. Zosky and P. H. Hart, Clinical & Experimental Allergy, 2010 (40) 772–785.     

Antigen-specific cytotoxic T lymphocytes target airway CD103+ and CD11b+ dendritic cells to suppress allergic inflammation

Allergic airway inflammation is driven by the recognition of inhaled allergen by T helper type 2 (Th2) cells in the airway and lung. Allergen-specific cytotoxic T lymphocytes (CTLs) can strongly reduce airway inflammation, however, the mechanism of their inhibitory activity is not fully defined. We used mouse models to show that allergen-specific CTLs reduced early cytokine production by Th2 cells in lung, and their subsequent accumulation and production of interleukin (IL)-4 and IL-13. In addition, treatment with specific CTLs also increased the proportion of caspase⁺ dendritic cells (DCs) in mediastinal lymph node (MLN), and decreased the numbers of CD103⁺ and CD11b⁺ DCs in the lung. This decrease required expression of the cytotoxic mediator perforin in CTLs and of the appropriate MHC-antigen ligand on DCs, suggesting that direct CTL-DC contact was necessary. Lastly, lung imaging experiments revealed that in airway-challenged mice XCR1-GFP⁺ DCs, corresponding to the CD103⁺ DC subset, and XCR1-GFP⁻ CD11c⁺ cells, which include CD11b⁺ DCs and alveolar macrophages, both clustered in the areas surrounding the small airways and were closely associated with allergen-specific CTLs. Thus, allergen-specific CTLs reduce allergic airway inflammation by depleting CD103⁺ and CD11b⁺ DC populations in the lung, and may constitute a mechanism through which allergic immune responses are regulated.     

Effect of bone marrow-derived CD11b+F4/80+ immature dendritic cells on the balance between pro-inflammatory and anti-inflammatory cytokines in DBA/1 mice with collagen-induced arthritis

Objective

To explore the effect of bone marrow-derived CD11b⁺F4/80⁺ immature dendritic cells (BM CD11b⁺F4/80⁺iDC) on the balance between pro-inflammatory and anti-inflammatory cytokines in DBA/1 mice with collagen-induced arthritis (CIA).

Methods

BM CD11b⁺F4/80⁺iDC were induced with rmGM-CSF and rmIL-4, and were identified by the expressions of toll-like receptor 2 (TLR-2), indoleamine 2,3-deoxygenase (IDO), interleukin (IL)-10, transforming growth factor (TGF)-β1 and mixed leukocyte reaction (MLR). CIA was established in DBA/1 mice by immunization with type II collagen. CIA mice were injected intravenously with BM CD11b⁺F4/80⁺iDC three times after immunization. The effect of BM CD11b⁺F4/80⁺iDC on CIA was evaluated by the arthritis index, joint histopathology, body weight, thymus index, thymocytes proliferation, IL-1β, tumor necrosis factor (TNF)-α, IL-17, IL-10 and TGF-β1 levels.

Results

BM CD11b⁺F4/80⁺iDC induced with rmGM-CSF and rmIL-4 expressed high levels of TLR-2, IDO, IL-10 and TGF-β1. Infusion of BM CD11b⁺F4/80⁺iDC in CIA mice significantly reduced the arthritis index and pathological scores of joints, recovered the weight, decreased the thymus index and inhibited thymocyte proliferation. Levels of IL-1β, TNF-α and IL-17 were decreased in BM CD11b⁺F4/80⁺iDC-treated mice.

Conclusions

BM CD11b⁺F4/80⁺iDC can be induced successfully with rmGM-CSF and rmIL-4. BM CD11b⁺F4/80⁺iDC treatment can ameliorate the development and severity of CIA by regulating the balance between pro-inflammatory cytokines and anti-inflammatory cytokines.     

Tumor‐induced CD11b+ Gr‐1+ myeloid‐derived suppressor cells exacerbate immune‐mediated hepatitis in mice in a CD40‐dependent manner

Immunosuppressive CD11b⁺Gr‐1⁺ myeloid‐derived suppressor cells (MDSCs) accumulate in the livers of tumor‐bearing (TB) mice. We studied hepatic MDSCs in two murine models of immune‐mediated hepatitis. Unexpectedly, treatment of TB mice with Concanavalin A (Con A) or α‐galactosylceramide resulted in increased alanine aminotransferase (ALT) and aspartate aminotransferase (AST) serum levels in comparison to tumor‐free mice. Adoptive transfer of hepatic MDSCs into naïve mice exacerbated Con A induced liver damage. Hepatic CD11b⁺Gr‐1⁺ cells revealed a polarized proinflammatory gene signature after Con A treatment. An IFN‐γ‐dependent upregulation of CD40 on hepatic CD11b⁺Gr‐1⁺ cells along with an upregulation of CD80, CD86, and CD1d after Con A treatment was observed. Con A treatment resulted in a loss of suppressor function by tumor‐induced CD11b⁺Gr‐1⁺ MDSCs as well as enhanced reactive oxygen species (ROS)‐mediated hepatotoxicity. CD40 knockdown in hepatic MDSCs led to increased arginase activity upon Con A treatment and lower ALT/AST serum levels. Finally, blockade of arginase activity in Cd40^?/? tumor‐induced myeloid cells resulted in exacerbation of hepatitis and increased ROS production in vivo. Our findings indicate that in a setting of acute hepatitis, tumor‐induced hepatic MDSCs act as proinflammatory immune effector cells capable of killing hepatocytes in a CD40‐dependent manner.     

The oral administration of bacterial extracts prevents asthma via the recruitment of regulatory T cells to the airways

The prevalence of asthma has steadily increased during the last decade, probably as the result of changes in the environment, including reduced microbial exposure during infancy. Accordingly, experimental studies have shown that deliberate infections with live pathogens prevent the development of allergic airway diseases in mice. Bacterial extracts are currently used in children suffering from repeated upper respiratory tract infections. In the present study, we have investigated whether bacterial extracts, commercially available as Broncho-Vaxom (BV), could prevent allergic airway disease in mice. Oral treatment with BV suppressed airway inflammation through interleukin-10 (IL-10)-dependent and MyD88 (myeloid differentiation primary response gene (88))-dependent mechanisms and induced the conversion of FoxP3 (forkhead box P3)⁻ T cells into FoxP3⁺ regulatory T cells. Furthermore, CD4⁺ T cells purified from the trachea of BV-treated mice conferred protection against airway inflammation when adoptively transferred into sensitized mice. Therefore, treatment with BV could possibly be a safe and efficient strategy to prevent the development of allergic diseases in children.     

The TLR4–TRIF pathway can protect against the development of experimental allergic asthma

The Toll‐like receptor (TLR) adaptor proteins myeloid differentiating factor 88 (MyD88) and Toll, interleukin‐1 receptor and resistance protein (TIR) domain‐containing adaptor inducing interferon‐β (TRIF) comprise the two principal limbs of the TLR signalling network. We studied the role of these adaptors in the TLR4‐dependent inhibition of allergic airway disease and induction of CD4⁺ ICOS⁺ T cells by nasal application of Protollin™, a mucosal adjuvant composed of TLR2 and TLR4 agonists. Wild‐type (WT), Trif^−/− or Myd88^−/− mice were sensitized to birch pollen extract (BPEx), then received intranasal Protollin followed by consecutive BPEx challenges. Protollin's protection against allergic airway disease was TRIF‐dependent and MyD88‐independent. TRIF deficiency diminished the CD4⁺ ICOS⁺ T‐cell subsets in the lymph nodes draining the nasal mucosa, as well as their recruitment to the lungs. Overall, TRIF deficiency reduced the proportion of cervical lymph node and lung CD4⁺ ICOS⁺ Foxp3⁻ cells, in particular. Adoptive transfer of cervical lymph node cells supported a role for Protollin‐induced CD4⁺ ICOS⁺ cells in the TRIF‐dependent inhibition of airway hyper‐responsiveness. Hence, our data demonstrate that stimulation of the TLR4‐TRIF pathway can protect against the development of allergic airway disease and that a TRIF‐dependent adjuvant effect on CD4⁺ ICOS⁺ T‐cell responses may be a contributing mechanism.     

Phenotypic, morphological, and functional heterogeneity of splenic immature myeloid cells in the host response to tularemia

Recent studies have linked accumulation of the Gr-1⁺ CD11b⁺ cell phenotype with functional immunosuppression in diverse pathological conditions, including bacterial and parasitic infections and cancer. Gr-1⁺ CD11b⁺ cells were the largest population of cells present in the spleens of mice infected with sublethal doses of the Francisella tularensis live vaccine strain (LVS). In contrast, the number of T cells present in the spleens of these mice did not increase during early infection. There was a significant delay in the kinetics of accumulation of Gr-1⁺ CD11b⁺ cells in the spleens of B-cell-deficient mice, indicating that B cells play a role in recruitment and maintenance of this population in the spleens of mice infected with F. tularensis. The splenic Gr-1⁺ CD11b⁺ cells in tularemia were a heterogeneous population that could be further subdivided into monocytic (mononuclear) and granulocytic (polymorphonuclear) cells using the Ly6C and Ly6G markers and differentiated into antigen-presenting cells following ex vivo culture. Monocytic, CD11b⁺ Ly6C^hi Ly6G⁻ cells but not granulocytic, CD11b⁺ Ly6C^int Ly6G⁺ cells purified from the spleens of mice infected with F. tularensis suppressed polyclonal T-cell proliferation via a nitric oxide-dependent pathway. Although the monocytic, CD11b⁺ Ly6C^hi Ly6G⁻ cells were able to suppress the proliferation of T cells, the large presence of Gr-1⁺ CD11b⁺ cells in mice that survived F. tularensis infection also suggests a potential role for these cells in the protective host response to tularemia.     

Expansion of CD11b+Ly-6C+ myeloid-derived suppressor cells (MDSCs) driven by galectin-9 attenuates CVB3-induced myocarditis

Galectin-9 is known to play a role in the modulation of innate and adaptive immunity to ameliorate CVB3-induced myocarditis. In the present study, we found that galectin-9 induced the expansion of CD11b⁺Ly-6C⁺ myeloid-derived suppressor cells (MDSCs) in the heart from CVB3-infected mice. Adoptive transfer of CD11b⁺Ly-6C⁺ MDSCs significantly alleviated myocarditis accompanied by increased Th2 and Treg frequency and anti-inflammatory cytokines expression in the heart tissue. Moreover, Ly6C⁺ MDSCs, but not Ly6G⁺ cells, expressed Arg-1 and NOS2, and suppressed CD4⁺ T cell proliferation in vitro in an Arg-1-dependent mechanism; an event that was reversed with treatment of either an Arg-1 inhibitor or addition of excess l-arginine. Furthermore, Ly6C⁺ MDSCs co-expressed higher levels of F4/80, Tim-3, and IL-4Rα, and had the plasticity to up-regulate NOS2 or Arg-1 in response to IFN-γ or IL-4 treatment. The present results indicate that galectin-9 expands CD11b⁺Ly-6C⁺ MDSCs to ameliorate CVB3-induced myocarditis.     

Glycyrrhizic Acid-Mediated Subdual of Myeloid-Derived Suppressor Cells Induces Antileishmanial Immune Responses in a Susceptible Host

CD11b⁺ Gr1⁺ myeloid-derived suppressor cells (MDSCs), a heterogeneous population of precursor cells, modulate protective immunity against visceral leishmaniasis by suppressing T cell functions. We observed that CD11b⁺ Gr1⁺ MDSCs, which initially expanded in soluble leishmanial antigen (SLA)-immunized mice and later diminished, suppressed proliferation of T cells isolated from SLA-immunized mice, but to a lesser extent than the case in naive mice. This lesser suppression of MDSCs accompanied the expression of F4/80 and the production of Cox-2, arginase I, nitric oxide, and PGE2. However, with SLA immunization, there was no difference in the expression of interleukin-2 (IL-2) or gamma interferon (IFN-γ) by T cells, in contrast to the case in nonimmunized mice, in which there is an influence. Glycyrrhizic acid (a triterpenoid compound)-mediated inhibition of Cox-2 in myeloid-derived suppressor cells influenced the capacity of T cells to proliferate and the expression of IL-2 and IFN-γ in Leishmania donovani-infected BALB/c mice. Further characterization confirmed that administration of glycyrrhizic acid to L. donovani-infected BALB/c mice results in an impairment of the generation of MDSCs and a reciprocal organ-specific proliferation of IFN-γ- and IL-10-expressing CD4⁺ and CD8⁺ T cells. Comprehensive knowledge on the Cox-2-mediated regulation of myeloid-derived suppressor cells might be involved in unlocking a new avenue for therapeutic interventions during visceral leishmaniasis.     

TET2 Regulates 5-Hydroxymethylcytosine Signature and CD4+ T-Cell Balance in Allergic Rhinitis

PurposePrevious studies have shown the role of ten-eleven translocation 2 (TET2) in CD4⁺ T cells. However, its function in CD4⁺ T cells under allergic inflammation is unclear. We aimed to investigate the epigenomic distribution of DNA 5-hydroxymethylcytosine (5hmC) and the role of TET2 in CD4⁺ T cells of allergic rhinitis (AR).MethodsThe hMeDIP-seq was performed to identify sequences with 5hmC deposition in CD4⁺ T cells of AR patients. Tet2-deficient or wild type mice were stimulated with ovalbumin (OVA) to develop an AR mouse model. The histopathology in nasal mucosae, Th1/Th2/Treg/Th17 cell percentage, concentrations of Th-related cytokines, expression of Tet and differential hydroxymethylated genes (DhMG), and the global deposition of 5hmC in sorted CD4⁺ T cells were detected.ResultsEpigenome-wide 5hmC landscape and DhMG in the CD4⁺ T cells of AR patients were identified. Tet2 depletion did not led to spontaneous inflammation. However, under the stimulation of allergen, OVA, loss of Tet2 resulted in the exacerbation of allergic inflammation, which was characterized by severer allergic symptoms, more inflammatory cells infiltrating the nasal lamina propria, sharper imbalances between Th1/Th2 and Treg/Th17 cells, and excessive secretion of OVA-specific IgE and Th2-related cytokines. Moreover, altered mRNA production of several DhMG and sharp decrease in 5hmC deposition were also observed in Tet2-deficient OVA-exposed mice.ConclusionsTET2 may regulate DNA 5hmC, DhMG expressions, and CD4⁺ T cell balance in AR.     

MMP induced by Gr‐1+ cells are crucial for recruitment of Th cells into the airways

Th2 lymphocytes deliver essential signals for induction of asthmatic airway inflammation. We previously found that airway antigen challenge induces recruitment of Gr‐1⁺ neutrophils prior to the recruitment of Th2 cells. We examined, therefore, whether Gr‐1⁺ cells contribute to the development of Th2‐dependent airway inflammation. Systemic depletion of Gr‐1⁺ cells using the RB6‐8C5 monoclonal antibody reduced Th2 cell recruitment following i.n. antigen challenge. The levels of both MMP‐9 and the tissue inhibitor of matrix metalloproteinases‐1 mRNA were up‐regulated in the lungs of mice 12 h after i.n. antigen challenge. Up‐regulation of tissue inhibitor of matrix metalloproteinases‐1 was independent of Gr‐1⁺ cells, whereas up‐regulation of MMP‐9 RNA and total gelatinolytic activity was dramatically reduced in mice depleted of Gr‐1⁺ cells. At 24 h after challenge, total lung collagenolytic activity was also up‐regulated, in a Gr‐1⁺ cell‐dependent fashion. Systemic inhibition of MMP‐8 and MMP‐9 reduced the airway recruitment of Th cells, resulting in significantly reduced eosinophilic inflammation. These data suggest that antigen challenge via the airway activates Gr‐1⁺ cells and consequently MMP to facilitate the recruitment of Th cells in the airway inflammatory response.     

Immunotherapy using lipopolysaccharide‐stimulated bone marrow‐derived dendritic cells to treat experimental autoimmune encephalomyelitis

Lipopolysaccharide (LPS) produced by Gram‐negative bacteria induces tolerance and suppresses inflammatory responses in vivo; however, the mechanisms are poorly understood. In this study we show that LPS induces apoptosis of bone marrow‐derived dendritic cells (DCs) and modulates phenotypes of DCs. LPS treatment up‐regulates expression of tolerance‐associated molecules such as CD205 and galectin‐1, but down‐regulates expression of Gr‐1 and B220 on CD11c⁺ DCs. Moreover, LPS treatment regulates the numbers of CD11c⁺CD8⁺, CD11c⁺CD11b^low and CD11c⁺CD11b^hi DCs, which perform different immune functions in vivo. Our data also demonstrated that intravenous transfer of LPS‐treated DCs blocks experimental autoimmune encephalomyelitis (EAE) development and down‐regulates expression of retinoic acid‐related orphan receptor gamma t (ROR‐γt), interleukin (IL)‐17A, IL‐17F, IL‐21, IL‐22 and interferon (IFN)‐γ in myelin oligodendrocyte glycoprotein (MOG)‐primed CD4⁺ T cells in the peripheral environment. These results suggest that LPS‐induced apoptotic DCs may lead to generation of tolerogenic DCs and suppress the activity of MOG‐stimulated effector CD4⁺ T cells, thus inhibiting the development of EAE in vivo. Our results imply a potential mechanism of LPS‐induced tolerance mediated by DCs and the possible use of LPS‐induced apoptotic DCs to treat autoimmune diseases such as multiple sclerosis.