The critical role of IL-12p40 in initiating,enhancing, and perpetuating pathogenic events in murine experimental autoimmune neuritis

Interleukin 12 (IL-12) is a proinflammatory cytokine with important immunoregulatory activities and is critical in determining the differentiation and generation of Th1 cells. For the present study, we investigated the role of endogenous IL-12 in the pathogenesis of experimental autoimmune neuritis (EAN), which is a CD4+ T-cell mediated autoimmune inflammatory disease of the peripheral nervous system. EAN is used as an animal model for Guillain-Barré syndrome of humans. Here, EAN was established in IL-12 p40 deficient mutant (IL-12-/-) C57BL/6 mice by immunization with P0 peptide 180-199, a purified component of peripheral nerve myelin, and Freund's complete adjuvant. In these IL-12-/- mice the onset of clinical disease was delayed, and the incidence and severity of EAN were significantly reduced compared to that in wild-type mice.The former group's clinical manifestations were associated with less P0-peptide 180-199 induced secretion of interferon-gamma (IFN-gamma) by splenocytes in vitro and low production of anti-P0-peptide 180-199 IgG2b antibodies in serum. Fewer IFN-gamma and TNF-alpha producing cells, but more cells secreting IL-4, were found in sciatic nerve sections from IL-12-/- mice, consistent with impaired Th1 functions and response. However, the IL-12 deficiency appeared not to affect P0 peptide 180-199-specific T-cell proliferation. These results indicate that IL-12 has a major role in the initiation, enhancement and perpetuation of pathogenic events in EAN by promoting a Th1 cell-mediated immune response and suppressing the Th2 response. This information augments consideration of IL-12 as a therapeutic target in Guillain-Barré syndrome and other T-cell-mediated autoimmune diseases.     

Induction by a lactic acid bacterium of a population of CD4(+) T cells with low proliferative capacity that produce transforming growth factor beta and interleukin-10.

We investigated whether certain strains of lactic acid bacteria (LAB) could antagonize specific T-helper functions in vitro and thus have the potential to prevent inflammatory intestinal immunopathologies. All strains tested induced various levels of both interleukin-12 (IL-12) and IL-10 in murine splenocytes. In particular, Lactobacillus paracasei (strain NCC2461) induced the highest levels of these cytokines. Since IL-12 and IL-10 have the potential to induce and suppress Th1 functions, respectively, we addressed the impact of this bacterium on the outcome of CD4(+) T-cell differentiation. For this purpose, bacteria were added to mixed lymphocyte cultures where CD4(+) T-cells from naive BALB/c mice were stimulated weekly in the presence of irradiated allogeneic splenocytes. In these cultures, L. paracasei NCC2461 strongly inhibited the proliferative activity of CD4(+) T cells in a dose-dependent fashion. This was accompanied by a marked decrease of both Th1 and Th2 effector cytokines, including gamma interferon, IL-4, and IL-5. In contrast, IL-10 was maintained and transforming growth factor beta (TGF-beta) was markedly induced in a dose-dependent manner. The bacteria were not cytotoxic, because cell viability was not affected after two rounds of stimulation. Thus, unidentified bacterial components from L. paracasei NCC2461 induced the development of a population of CD4(+) T cells with low proliferative capacity that produced TGF-beta and IL-10, reminiscent of previously described subsets of regulatory cells implicated in oral tolerance and gut homeostasis.     

IL-27, targeting antigen-presenting cells,promotes Th17 differentiation and colitis in mice

T helper type 17 (Th17) cells have been implicated in autoimmunity and inflammatory bowel disease (IBD). Antigen-presenting cell (APC) -derived cytokines such as interleukin (IL)-1β and IL-6 are key mediators supporting Th17 differentiation, yet how these factors are induced in vivo remains unclear. Here, we show that IL-27 acting on APCs enhances IL-6 and IL-1β production and Th17 differentiation. IL-27Rα−/− T-cell receptor (TCR)β−/− recipients fail to develop gut inflammation following naive CD4 T-cell transfer, whereas IL-27Rα+/+ TCRβ−/− recipients develop severe colitis. Investigation of T-cell responses exhibits that IL-27Rα−/− TCRβ−/− mice do not support Th17 differentiation with significantly decreased levels of IL-6 and IL-1β by APCs. Our study has identified a novel proinflammatory role for IL-27 in vivo that promotes Th17 differentiation by inducing Th17-supporting cytokines in APCs.     

Short-term heat exposure inhibits inflammation by abrogating recruitment of and nuclear factor-{kappa}B activation in neutrophils exposed to chemotactic cytokines

Cytokines, such as granulocyte macrophage-colony stimulating factor (GM-CSF) and interleukin (IL)-8 attract neutrophils into inflammatory sites. During emigration from the blood neutrophils interact with extracellular matrix proteins such as fibronectin. Fibronectin provides beta2-integrin co-stimulation, allowing GM-CSF and IL-8 to activate nuclear factor (NF)-kappaB, an effect that does not occur in suspension. We tested the hypothesis that exposure of mice to fever-like temperatures abrogates neutrophil recruitment and NF-kappaB activation in a mouse model of skin inflammation. Mice that were exposed to 40 degrees C for 1 hour showed strongly reduced GM-CSF- and IL-8-induced neutrophilic skin inflammation. In vitro heat exposure did not interfere with neutrophil adhesion or spreading on fibronectin but strongly inhibited migration toward both cytokines. Using specific inhibitors, we found that PI3-K/Akt was pivotal for neutrophil migration and that heat down-regulated this pathway. Furthermore, neutrophils on fibronectin showed abrogated NF-kappaB activation in response to GM-CSF and IL-8 after heat. In vivo heat exposure of mice followed by ex vivo stimulation of isolated bone marrow neutrophils confirmed these results. Finally, less NF-kappaB activation was seen in the inflammatory lesions of mice exposed to fever-like temperatures as demonstrated by in situ hybridization for IkappaBalpha mRNA. These new findings suggest that heat may have anti-inflammatory effects in neutrophil-dependent inflammation.     

Phlebotomine salivas inhibit immune inflammation-induced neutrophil migration via an autocrine DC-derived PGE2/IL-10 sequential pathway

In the present study, we investigated whether saliva from Phlebotomus papatasi and Phlebotomus duboscqi inhibited antigen-induced neutrophil migration and the mechanisms involved in these effects. The pretreatment of immunized mice with salivary gland extracts (SGE) of both phlebotomines inhibited OVA challenge-induced neutrophil migration and release of the neutrophil chemotactic mediators, MIP-1alpha, TNF-alpha, and leukotriene B4 (LTB4). Furthermore, SGE treatment enhanced the production of anti-inflammatory mediators, IL-10 and PGE2. SGE treatments failed to inhibit neutrophil migration and MIP-1alpha and LTB4 production in IL-10-/- mice, also failing in mice treated with nonselective (indomethacin) or selective (rofecoxibe) cyclooxygenase (COX) inhibitors. COX inhibition resulted in diminished SGE-induced IL-10 production, and PGE2 release triggered by SGE remained increased in IL-10-/- mice, suggesting that prostanoids are acting through an IL-10-dependent mechanism. SGE treatments in vivo reduced the OVA-induced lymphoproliferation of spleen-derived cells. Further, the in vitro incubation of bone marrow-derived dendritic cells (DC) with SGE inhibited the proliferation of CD4+T cells from OVA-immunized mice, which was reversed by indomethacin and anti-IL-10 antibody treatments. Supporting these results, SGE induced the production of PGE2 and IL-10 by DC, which were blocked by COX inhibition. These effects were associated with the reduction of DC-membrane expression of MHC-II and CD86 by SGE treatment. Altogether, the results showed that Phlebotomine saliva inhibits immune inflammation-induced neutrophil migration by an autocrine DC sequential production of PGE2/IL-10, suggesting that the saliva constituents might be promising therapeutic molecules to target immune inflammatory diseases.     

Multiformic modulation of endotoxin effects by linomide

Linomide is a potent immunomodulator that either enhances or suppresses certain immunological processes. Of particular interest is this compound's capacity to inhibit a variety of organ-specific autoimmune diseases. Here, we report on the effects of linomide on several immunological reactions elicited by endotoxin (LPS), both in vivo and in vitro. In rats and mice linomide inhibited the elicitation of endotoxin-induced uveitis (EIU), an acute inflammatory eye disease that develops within 24 h following footpad injection of LPS. Linomide also inhibited the production of TNF-alpha and IL-6 by LPS-stimulated rat and mouse macrophage monolayers. On the other hand, treatment with linomide significantly increased the levels of IL-1beta (mice and less in rats), IL-6 (rats), and TNF-alpha (mice) in serum samples collected 2 h following injection with LPS. The increased production of proinflammatory cytokines in linomide-treated mice was also indicated by the enhanced lethal effect of LPS in these mice. The finding of elevated levels of these cytokines in animals with suppressed EIU is also in line with previous observations of an inverse relationship between EIU severity and levels of TNF-alpha. Data recorded here underscore the unique capacity of linomide to both enhance and suppress the immune system.     

Role of interleukin-4 in down-regulation of contact sensitivity by gammadelta T cells from tolerized T-cell receptor alpha-/- mice.

Contact sensitivity (CS) is a classical example of an in vivo T-cell-mediated immune response that is under regulation. Such down-regulation can be mediated by alphabeta T cells in mice that are tolerized by prior exposure to high doses of antigen. In contrast, we demonstrated previously that such high-dose antigen tolerance in T-cell receptor (TCR) alpha-/- H-2d mice induced antigen-specific, apparently major histocompatibility complex-unrestricted, CD4- CD8- gammadelta T cells, that also could down-regulate CS responses antigen-specifically in vivo, and also inhibited in vitro production of IFN-gamma. In the present experiments we employed H-2b-deficient TCRalpha-/- and TCRbeta-/- mice, owing to different molecular constructs than were used previously, and confirmed that tolerized gammadelta T cells in these different H-2b alphabeta TCR-/- mice down-regulated CS. Thus, gammadelta T-cell suppressor function was not limited to mice bearing a special transgenic TCRalpha-/- DNA construct. Furthermore, employing monoclonal antibody and complement depletion in vitro and adoptive transfer in vivo, characterized the phenotype of these gammadelta down-regulatory T cells as: CD3+, CD28+, CD40-ligand+, Fas+, FcgammaR+ and NK1.1-. Also, in vitro antigen desensitization of these trinitrophenyl (TNP)-specific TCRgammadelta+ down-regulatory cells was achieved with soluble TNP-bovine serum albumin (BSA), but not with oxazolone-BSA, showing that these suppressive gammadelta T cells have antigen-specific receptors. Moreover, employing monoclonal antibody blocking of gammadelta suppressors in vitro, and of recipients in vivo, we showed that interleukin-4 (IL-4) was involved in this down-regulation of CS by gammadelta T cells, while IL-10 and transforming growth factor-beta2 were not. In summary, generation of antigen-specific, double-negative, gammadelta suppressor cells, by tolerance of high antigen doses in TCRalpha-/- mice, appears to be a general phenomenon, and IL-4 production is involved in their down-regulation of the T helper type 1 cells that mediate CS.     

Retinoic acid prevents mesenteric lymph node dendritic cells from inducing IL-13-producing inflammatory Th2 cells

The vitamin A (VA) metabolite retinoic acid (RA) affects the properties of T cells and dendritic cells (DCs). In VA-deficient mice, we observed that mesenteric lymph node (MLN)-DCs induce a distinct inflammatory T helper type 2 (Th2)-cell subset that particularly produces high levels of interleukin (IL)-13 and tumor necrosis factor-α (TNF-α). This subset expressed homing receptors for skin and inflammatory sites, and was mainly induced by B220⁻CD8α⁻CD11b⁺CD103⁻ MLN-DCs in an IL-6- and OX40 ligand-dependent manner, whereas RA inhibited this induction. The corresponding MLN-DC subset of VA-sufficient mice induced a similar T-cell subset in the presence of RA receptor antagonists. IL-6 induced this subset differentiation from naive CD4⁺ T cells upon activation with antibodies against CD3 and CD28. Transforming growth factor-β inhibited this induction, and reciprocally enhanced Th17 induction. Treatment with an agonistic anti-OX40 antibody and normal MLN-DCs enhanced the induction of general inflammatory Th2 cells. In VA-deficient mice, proximal colon epithelial cells produced TNF-α that may have enhanced OX40 ligand expression in MLN-DCs. The repeated oral administrations of a T cell-dependent antigen primed VA-deficient mice for IL-13-dependent strong immunoglobulin G1 (IgG1) responses and IgE responses that caused skin allergy. These results suggest that RA inhibits allergic responses to oral antigens by preventing MLN-DCs from inducing IL-13-producing inflammatory Th2 cells.     

Licochalcone A isolated from licorice suppresses lipopolysaccharide-stimulated inflammatory reactions in RAW264.7 cells and endotoxin shock in mice

Licochalcone A (LicA), a major phenolic constituent of the licorice species Glycyrrhiza inflata, exhibits various biological properties, including chemopreventive, anti-bacterial, and anti-spasmodic activity. We report that LicA inhibits inflammatory reactions in macrophages and protects mice from endotoxin shock. Our in vitro experiments showed that LicA suppressed not only the generation of nitric oxide (NO) and prostaglandin (PG)E(2), but also the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2 induced by lipopolysaccharide (LPS) in RAW264.7 cells. Similarly, LicA inhibited the production of inflammatory cytokines induced by LPS in RAW264.7 cells, including IL-1 beta and IL-6. In an animal model, LicA protected BALB/c mice from LPS-induced endotoxin shock, possibly through inhibiting the production of inflammatory cytokines and NO. Collectively, LicA inhibited the production of inflammatory mediators and may be a potential target for treatment of various inflammatory diseases.     

Heligmosomoides polygyrus promotes regulatory T-cell cytokine production in the murine normal distal intestine

Helminths down-regulate inflammation and may prevent development of several autoimmune illnesses, such as inflammatory bowel disease. We determined if exposure to the duodenal helminth Heligmosomoides polygyrus establishes cytokine pathways in the distal intestine that may protect from intestinal inflammation. Mice received 200 H. polygyrus larvae and were studied 2 weeks later. Lamina propria mononuclear cells (LPMC) were isolated from the terminal ileum for analysis and in vitro experiments. Mice with H. polygyrus were resistant to trinitrobenzenesulfonic acid (TNBS)-induced colitis, a Th1 cytokine-dependent inflammation. Heligmosomoides polygyrus did not change the normal microscopic appearance of the terminal ileum and colon and minimally affected LPMC composition. However, colonization altered LPMC cytokine profiles, blocking gamma interferon (IFN-gamma) and interleukin 12 (IL-12) p40 release but promoting IL-4, IL-5, IL-13, and IL-10 secretion. IL-10 blockade in vitro with anti-IL-10 receptor (IL-10R) monoclonal antibody restored LPMC IFN-gamma and IL-12 p40 secretion. IL-10 blockade in vivo worsened TNBS colitis in H. polygyrus-colonized mice. Lamina propria CD4(+) T cells isolated from colonized mice inhibited IFN-gamma production by splenic T cells from worm-free mice. This inhibition did not require cell contact and was dependent on IL-10. Heligmosomoides polygyrus colonization inhibits Th1 and promotes Th2 and regulatory cytokine production in distant intestinal regions without changing histology or LPMC composition. IL-10 is particularly important for limiting the Th1 response. The T-cell origin of these cytokines demonstrates mucosal regulatory T-cell induction.     

Phosphatidylinositol 3-kinase inhibitors prevent mouse cytotoxic T-cell development in vitro

To become competent killer cells, CD8(+) T cells require stimulation through signal transduction pathways associated with the T-cell receptor, costimulatory molecules such as CD28, and cytokine receptors such as the interleukin (IL)-2 receptor. We used wortmannin and LY294002, two inhibitors of phosphatidylinositol 3-kinase (PI3-K), to study the role of PI3-K in mouse cytotoxic T-lymphocyte (CTL) induction in response to mitogenic anti-CD3 antibody. Anti-CD3-induced CD8(+) T-cell proliferation and CTL development were inhibited dose dependently by both PI3-K inhibitors. IL-2 synthesis by anti-CD3-activated CD8(+) T cells was also diminished by PI3-K inhibition. PI3-K inhibition resulted in a modest decrease in anti-CD3-induced CD4(+) T-cell proliferation but failed to affect IL-2 expression by anti-CD3-activated CD4(+) T cells. PI3-K inhibition during CTL induction resulted in decreased levels of mRNAs coding for granzyme B, perforin, and Fas ligand. In addition, CTL induced in the presence of PI3-K inhibitors failed to conjugate normally with P815 target cells. Exogenous IL-2 did not reverse the effects of PI3-K inhibition on CD8(+) T-cell proliferation and CTL induction. These results support the conclusion that PI3-K activation is involved in T-cell receptor, CD28, and IL-2 receptor signaling of CD8(+) T cells. PI3-K is, therefore, an important component of multiple signal transduction pathways involved in CTL generation.     

大气颗粒物急性暴露对C57BL/6小鼠肺脏病理改变和气道上皮细胞IL-6和IL-8表达的影响

目的:探讨大气颗粒物(PM)急性暴露下C57BL/6小鼠肺脏的病理改变和气道上皮细胞炎症介质白细胞介素6(IL-6)和白细胞介素8(IL-8)分泌的分子机制.方法:选取雄性C57BL/6小鼠随机分为空白对照组和PM实验组,每组10只:PM实验组连续2 d经气管滴注PM悬浮液,建立PM短期暴露的小鼠模型;空白对照组连续2...     

Induction by a Lactic Acid Bacterium of a Population of CD4+ T Cells with Low Proliferative Capacity That Produce Transforming Growth Factor β and Interleukin-10

We investigated whether certain strains of lactic acid bacteria (LAB) could antagonize specific T-helper functions in vitro and thus have the potential to prevent inflammatory intestinal immunopathologies. All strains tested induced various levels of both interleukin-12 (IL-12) and IL-10 in murine splenocytes. In particular, Lactobacillus paracasei (strain NCC2461) induced the highest levels of these cytokines. Since IL-12 and IL-10 have the potential to induce and suppress Th1 functions, respectively, we addressed the impact of this bacterium on the outcome of CD4⁺ T-cell differentiation. For this purpose, bacteria were added to mixed lymphocyte cultures where CD4⁺ T-cells from naive BALB/c mice were stimulated weekly in the presence of irradiated allogeneic splenocytes. In these cultures, L. paracasei NCC2461 strongly inhibited the proliferative activity of CD4⁺ T cells in a dose-dependent fashion. This was accompanied by a marked decrease of both Th1 and Th2 effector cytokines, including gamma interferon, IL-4, and IL-5. In contrast, IL-10 was maintained and transforming growth factor β (TGF-β) was markedly induced in a dose-dependent manner. The bacteria were not cytotoxic, because cell viability was not affected after two rounds of stimulation. Thus, unidentified bacterial components from L. paracasei NCC2461 induced the development of a population of CD4⁺ T cells with low proliferative capacity that produced TGF-β and IL-10, reminiscent of previously described subsets of regulatory cells implicated in oral tolerance and gut homeostasis.     

Linkage analysis of the genetic determinants of T-cell IL-4 secretion, and identification of Flj20274 as a putative candidate gene

The activation-induced differentiation of naive CD4+ T cells generates functionally divergent type 1 helper T cells (Th1) or type 2 helper T cells (Th2) effector cell populations, characterized by secretion of Interferon (IFN)-gamma or Interleukin (IL)-4, respectively. Inappropriate generation of Th subsets may contribute to immune dysfunction. The decision to generate Th1/Th2 lineages is critically regulated by cytokines, such that IL-12 induces Th1 differentiation, while IL-4 induces Th2 differentiation. Genetic factors influence the pathway of Th differentiation, as displayed by the preferential generation of divergent Th populations by different inbred strains of mice. We employ two complementary genetic techniques to identify genes that regulate the default IL-4 secretion profiles of T cells from BALB/c and B6 mice. We performed a genome-wide linkage analysis of the progeny of a backcross between BALB/c and B6 mice to identify three loci, T-cell secretion of interleukin-4 (Tsi)1-3, on chromosomes 7, 19 and 15, respectively, which regulate in vitro T-cell IL-4 production. We have also employed mRNA representational difference analysis to isolate a gene, Flj20274, which is differentially expressed in T cells that secrete high levels of IL-4. Significantly, Flj20274 was mapped to the point of peak linkage within Tsi1 and is a strong candidate for Tsi1.     

Modification of in vivo and in vitro T- and B-cell-mediated immune responses by the Pseudomonas aeruginosa quorum-sensing molecule N-(3-oxododecanoyl)-L-homoserine lactone

N-3-(oxododecanoyl)-L-homoserine lactone (OdDHL), a quorum-sensing molecule of Pseudomonas aeruginosa, plays an important role in the pathogenesis of the organism through its control of virulence factor expression. Several reports have suggested that OdDHL can also directly modulate host immune responses. However, the nature of the modulation is controversial, with different reports suggesting promotion of either humoral (Th2-mediated) or inflammatory (Th1-mediated) responses. This report describes a series of studies which demonstrate for the first time that in vivo administration of OdDHL can modulate the course of an antibody response, with an increase in ovalbumin (OVA)-specific immunogloblulin G1 (IgG1) but not IgG2a in OdDHL-treated OVA-immunized BALB/c mice compared to levels for controls. In vitro stimulation of lymphocytes from both Th1-biased C57Bl/6 and T-cell receptor transgenic mice and Th2-biased BALB/c mice in the presence of OdDHL demonstrated that OdDHL inhibits in vitro cytokine production in response to both mitogen and antigen, with gamma interferon (IFN-gamma) tending to be more inhibited than interleukin-4 (IL-4). In vitro mitogen or antigen restimulation of cells from mice treated with OdDHL in vivo shows effects on cytokine production which depend on the underlying immune bias of the mouse strain used, with a relative increase of IFN-gamma in Th1-biased C57Bl/6 mice and a relative increase of IL-4 in Th2-biased BALB/c mice. Thus, the mode of action of OdDHL on T-cell cytokine production is likely to be a relatively nonspecific one which accentuates an underlying immune response bias rather than one which specifically targets either Th1 or Th2 responses.     

Tolerogenic dendritic cells pulsed with enterobacterial extract suppress development of colitis in the severe combined immunodeficiency transfer model

Immunomodulatory dendritic cells (DCs) that induce antigen-specific T-cell tolerance upon in vivo adoptive transfer are promising candidates for immunotherapy of autoimmune diseases. The feasibility of such a strategy has recently proved its efficacy in animal models of allotransplantation and experimental allergic encephalitis, but the effect in inflammatory bowel disease has not yet been demonstrated. In severe combined immunodeficient (SCID) mice, adoptively transferred CD4(+) CD25(-) T cells repopulate the lymphoid tissues and lead to development of chronic colitis characterized by CD4(+) T-cell proliferation against enterobacterial extract in vitro. In this model, we adoptively transferred in-vitro-generated bone-marrow-derived DCs exposed to interleukin-10 (IL-10) and an enterobacterial extract. We show that these cells are CD11c positive with intermediate expression of CD40, CD80 and CD86 and have a diminished secretion of IL-6, IL-12 p40/70, tumour necrosis factor-alpha and keratinocyte-derived chemokine (KC) compared to DCs treated with enterobacterial extract alone. In vivo, these cells prevented weight loss in SCID mice adoptively transferred with CD4(+) CD25(-) T cells, resulted in a lower histopathology colitis score and tended to result in higher serum levels of IL-1alpha, IL-10, IL-12, IL-13, IL-17, KC and monokine induced by interferon-gamma (MIG). These data underscore the potential of using immunomodulatory DCs to control inflammatory bowel disease and demonstrate its potential use in future human therapeutic settings.     

Reduced susceptibility to dextran sulphate sodium-induced colitis in the interleukin-2 heterozygous (IL-2) mouse

Summary Mice homozygous for an inactivation of the interleukin-2 (IL-2) gene develop a T-cell dependent colitis. Heterozygous (IL-2+/-) mice are clinically healthy but have been shown to express reduced levels of IL-2 in the colon. Splenocytes from the IL-2+/- mice had a poorer proliferative response to polyclonal T-cell activation and these mice have reduced numbers of intestinal regulatory T cells (CD4+ CD25+ cells) when compared to wild type mice. When exposed to dextran sulphate sodium (DSS) IL-2+/- mice showed a markedly reduced susceptibility to DSS-induced colitis. While DSS treatment caused a marked increase in both CD4+ and CD8+ colonic T cells expressing increased levels of IL-2, IL-4, and IL-10 in wild type mice none of these changes were seen in IL-2+/- mice. On the contrary, cytokine expression in intestinal T cells of IL-2+/- mice was actually reduced after DSS treatment. These results suggest that reduced levels of IL-2 leads to attenuated activation and function of intestinal T cells in IL-2+/- mice and a failure to react adequately to DSS exposure.     

Immunomodulatory effects of aqueous birch pollen extracts and phytoprostanes on primary immune responses in vivo

BACKGROUND: We recently demonstrated that pollen not only function as allergen carriers but also as rich sources of bioactive lipids, such as phytoprostanes, that modulate human dendritic cell (DC) function in a way that results in an enhanced T(H)2 polarization in vitro. OBJECTIVE: Here we analyzed the immunomodulatory capacities of Betula alba (white birch) aqueous pollen extracts (Bet-APEs) and pollen-associated phytoprostanes in the murine system in vitro and in vivo. METHODS: DC function was analyzed in vitro by using BALB/c bone marrow-derived DCs. T-cell responses were analyzed with DO11.10 peptide 323-339 from chicken ovalbumin (OVA)-specific CD4 T cells as responder cells. For in vivo studies, OVA-specific CD4 T cells were adoptively transferred into BALB/c mice. Twenty-four hours later, mice were challenged by means of intranasal application of OVA in the absence or presence of Bet-APEs or phytoprostanes. Polarization of T-cell responses in vivo was analyzed in draining lymph node cells. RESULTS: In vitro Bet-APEs and E(1)-phytoprostanes dose-dependently inhibited LPS-induced IL-12p70 of DCs. In addition, Bet-APEs induced a T(H)2 polarization in vitro. Similarly, intranasal instillation of Bet-APEs in vivo, together with the antigen, lead to increased IL-4, IL-5, and IL-13 secretion and decreased IFN-gamma secretion from antigen-specific T cells in the draining lymph nodes. In contrast, intranasal E1- and F1-phytoprostanes downregulated both T(H)1 and T(H)2 cytokine production in vivo. CONCLUSION: Pollen release water-soluble factors that display T(H)2-polarizing capacities in vivo independently of E(1)- and F(1)-phytoprostanes. CLINICAL IMPLICATIONS: Identification of the underlying mechanisms might open new approaches for pharmacologic intervention.