Tu1882

FC Gamma Receptors Modulate the Inhibitory Efficacy of Infliximab inBlocking TNF-Mediated Responses in Blood and Intestine of IBD PatientsKacper A. Wojtal, Gerhard Rogler, Luc Biedermann, Pascal Frei, Michael Fried, StephanR. Vavricka

Background & Aims: Tumor necrosis factor (TNF) is an important cytokine in the pathogen-esis of inflammatory bowel disease (IBD). Anti-TNF drugs have been implemented in IBDtherapy. The efficacies of those drugs differ among individuals and they have not been testedin different tissues. The aim of this study was to evaluate their efficacies in ex vivo-treatedperhipheral blood and intestine of both IBD patients and healthy individuals. Methods:Peripheral blood obtained from healthy donors and IBD patients was used for stimulationexperiments with anti-TNF drugs. Peripheral blood mononuclear cells (PBMCs) were isolatedand the efficacies of anti-TNFs were assessed by RT-PCR and ELISA. Expression levels ofFc receptors were examined by Western blotting and RT-PCR. To determine the activationof Fc receptors we measured the production of GM-CSF and CCL-2 mRNAs and phospho-tyrosine signal in THP-1 cells. The expression levels of Fc receptors in human intestinaltissues and in PBMCs were determined by RT-PCR and Western blotting. Results: Bothadalimumab (ADA) and infliximab (IFX) displayed significant limitations in blocking TNF-mediated responses in ex vivo-treated peripheral blood from healthy donors as comparedto certolizumab-pegol (CZP; p<0.001). ADA had significantly lower efficacy in PBMCs ascompared to THP-1 cells (p<0.001), which was correlated with the increased expressionlevels of both low affinity Fc receptors CD16 and CD32. IFX, but no other anti-TNFs testedwas less effective in peripheral blood of IBD patients as compared to healthy controls(p<0.05) when assessed by measuring the changes on mRNA levels of IL-8, TNF and ICAMas well as plasma release of IL-8 (p<0.05). These differences were correlated with an increasein mRNA levels of both low affinity Fc receptors CD16 and CD32 in PBMCs from IBDpatients as compared to healthy individuals. In THP-1 cells IFX either alone or in complexwith TNF, was more potent in activating Fc receptors as measured by the production ofGM-CSF and CCL-2 mRNA (p<0.05). IFX/TNF but not ADA/TNF complexes induced IL-8 mRNA production in THP-1 cells (p<0.05), which was accompanied by detection ofdistinct phospho-tyrosine signals. Increased colonic mRNA (p<0.05) and protein (p<0.001)expression levels of CD64 as well as mRNA levels of CD16 (p<0.001) were detected ininflamed tissues of IFX-non-responders as compared to IFX responders. These changes werecorrelated with elevated mRNA levels of cytokines regulating the expression of this receptor,namely GM-CSF (p<0.01) and IFN-γ (p<0.0001) as well as IL-8 (p<0.0001) and IL-6(p<0.05). Conclusions: Fc receptors modulate the efficacy of IFX both ex- and In Vivo. Theseobservations will help to optimize individual anti-TNF strategy in IBD patients with elevatedsystemic and local levels of Fc receptors. Keywords: Fc receptor, anti-TNFs, peripheral blood

Tu1883

Activation of the Nuclear Receptor FXR by Oral Chenodeoxycholic Acid inPatients With Crohn's Colitis: Potential Therapeutic Consequences forInflammatory Bowel DiseaseFiona D. van Schaik, Raffaella Maria Gadaleta, Frank G. Schaap, Saskia W. van Mil, PeterD. Siersema, Bas Oldenburg, Karel J. Van Erpecum

Background: The bile salt nuclear receptor Farnesoid X Receptor (FXR), expressed in ileumand liver, is critical in preventing bacterial overgrowth and maintaining intestinal barrier.FXR activation by (semi-)synthetic agonists prevents inflammation in murine colitis models,probably by NFκB inhibition (Gut;2011;60:463-72). Patients with Crohn's colitis (CC)exhibit reduced ileal FXR target gene mRNA expression compared to patients with ulcerativecolitis and controls, suggesting impaired FXR activity in CC (PLoS One 2011;6:e23745).We investigated whether pharmacological FXR activation is feasible in CC. Methods: Ninepatients with quiescent CC and 12 controls were treated with the FXR ligand chenodeoxych-olic acid (CDCA,15 mg/kg/day) for 8 days. Ileal FXR activation was assessed in fasting statebefore and each hour during 6 hours after the first CDCA dosage and after the final dosageby quantification of serum levels of FGF19 (enterokine whose expression is controlled byFXR; by ELISA). Since FGF19 induces gallbladder (GB) refilling in the mouse, we alsodetermined GB volumes (by sonography). Ileal and cecal biopsies were obtained duringcolonoscopy after the last dosage, RNAwas isolated, and FXR and FXR target genes expressionanalysed with quantitative real time PCR. Results: At baseline, fasting FGF19 levels did notdiffer between CC and controls (0.23±0.14 vs 0.21±0.11 ng/mL, mean±SD). After the firstCDCA dosage, FGF19 and GB volumes initially decreased in both CC and controls (after1 hour: FGF19 30 resp. 31% of basal and GB volume: 12 resp. 15% of basal), with subsequentprogressive increases during the next 6 hours (FGF19: 537 resp. 576%; GB volume: 178resp. 190%) without differences between both groups, and further increases at day 8. Afterthe final CDCA dosage FGF19 levels and GB volumes correlated significantly in controls(r=0.60, p=0.04) but not in CC (r=0.32, p=0.41). Analysis of ileal biopsies from untreatedcontrols and from CDCA treated groups revealed that CDCA increased mRNA levels of FXRtarget genes IBABP (3.2 resp. 4.2 fold) and FGF19 (22 resp. 43 fold) and decreased mRNAlevels of ASBT (0.46 resp. 0.58 fold) to a similar extent in CC and controls, compared tountreated controls. SHP expression was only increased in CC (2.3 fold). Regarding FXR-dependent genes implicated in antibacterial defense: ileal and cecal angiogenin 1 mRNAexpression decreased (0.38 resp. 0.63 fold) in both CDCA treated groups. iNOS expressionwas not affected by CDCA treatment. mRNA expression of FXR and FXR target genes incecum was much lower than in ileum, without differences between CDCA treated CC andcontrols. Conclusion: Current results show that pharmacological activation of FXR is feasiblein patients with CC and provide a rationale to explore the anti-inflammatory properties ofpharmacological activation of FXR in these patients.

S-869 AGA Abstracts

Tu1884

Carrageenan Exposure Stimulates BCL10 - NF-KappaB - BCL10 Loop andProlonged Inflammation in Colonic Epithelial CellsAlip Borthakur, Sumit Bhattacharyya, Arivarasu Natarajan Anbazhagan, Anoop Kumar,Pradeep K. Dudeja, Joanne K. Tobacman

Carrageenan, a sulfated polysaccharide that is widely used as a food additive, is well-knownto provoke inflammatory responses in animal models and human cells. Carrageenan-inducedinflammatory cascades involve toll-like receptor(TLR)4/B-cell CLL/lymphoma(BCL)10- orreactive oxygen species- dependent activation of NF-kappaB, and increase Interleukin (IL)-8 secretion and impair insulin signaling. Translocations that lead to overexpression of BCL10in themucosa-associated lymphoid tissue (MALT) lymphomas are associated with constitutiveactivation of NF-kappaB. The sustained inflammatory response is of etiologic significancein the development of the lymphomas. Since prior studies demonstrated that carrageenanexposure increased BCL10 expression and BCL10 mediated canonical and non-canonical NF-kappaB activation, we investigated themolecular mechanisms involved, noting the presence ofan NF-kappaB binding consensus motif in the BCL10 promoter. Binding studies wereperformed in the human colonic epithelial cell lines, NCM460 and HT-29, and comparedbinding of RelA and RelB to the known NF-kappaB consensus sequence (5'-GGGACTTTCC-3'), the putative binding sequence in the BCL10 promoter (5'-GGAAACGCCC-3'), and amutated version of the sequence in the BCL10 promoter (5'-GTCCACGCCC-3') by In Vitrooligonucleotide binding assay, non-radioactive gel shift assay, and chromatin immunoprecip-itation (ChIP). Both RelA and RelB bound to the NF-kappaB consensus motif in the BCL10promoter, but not to mutated or scrambled sequences. Extent of binding was increasedfollowing carrageenan exposure. Sustained activation of the BCL10-NF-kappaB inflammatoryloop in response to carrageenan was demonstrated in NCM460 and HT-29 cells by measure-ments of BCL10, RelA, RelB, and IL-8 following withdrawal of carrageenan. BCL10, RelA,and IL-8 were significantly increased for 24-36 hours and RelB for 12 hours after withdrawalof carrageenan in both cell lines. In contrast, exposure to dextran sulfate sodium, whichdoes not cause inflammation through TLR4 and BCL10 in the colonic epithelial cells, didnot provoke prolonged activation of inflammation. The carrageenan-induced increases inBCL10, but not in phospho-BCL10, were inhibited by caffeic acid phenethyl ester (CAPE)and MG-132 which inhibit NF-kappaB nuclear translocation. The study results indicatethat NF-kappaB binding to the BCL10 promoter can lead to sustained stimulation of thecarrageenan-induced inflammatory cascade by prolonged activation of an inflammatory loopinvolving BCL10 and NF-kappaB.

Tu1885

Pregnane X Receptor Stimulation Reduces NF-κB Mediated CytokineExpression in Intestinal Biopsies From Inflammatory Bowel Disease PatientsJ. Jasper Deuring, Timon Q. van den Berg, Ernst J. Kuipers, Maikel P. Peppelenbosch,Colin de Haar, Christien J. van der Woude

Background and Aim: Mucosal detoxification of various anti-inflammatory drugs is mediatedamongst others by nuclear receptors like the Pregnane X Receptor (PXR). The activation ofPXR is associated with down regulation of nuclear-factor κ-B (NF-κB) activity, which playsa key role in inflammation. Here, we studied whether PXR activation could reduce NF-κB-mediated inflammatory responses in intestinal biopsies from inflammatory bowel disease(IBD) patients. Methods: Three biopsies were taken from four different bowel locations inIBD (n=26) and control patients (n=8). Biopsies from endoscopically inflamed and non-inflamed areas were included and inflammation was histologically confirmed by an expertpathologist. The biopsies were cultured for 18 h with or without PXR activator Rifampicin(100μM). Rifampicin-induced PXR activation was verified by the mRNA expression of PXRtarget genes (Cyp3A4, Sult1a, MDR1) and the possible repression of NF-κB by the expressionof its target genes (IL-8, IL-1β, TNFα). In addition, the protein expression of TNFα andIL-8 in biopsy homogenates wasmeasured using ELISA. Results: The gene expression of Sult1aand MDR1 are up-regulated in all the biopsies after Rifamipcin stimulation. Furthermore, theexpression of IL-8 (p<0.001) and IL-1β (p<0.01) are 10-100 fold higher in biopsies fromIBD patients than in biopsies from control patients, irrespective of disease activity. However,this elevated cytokine expression was significantly reduced after Rifampicin stimulation(p<0.01). This reduction is observed in all biopsies on mRNA as well as protein expressionand is regardless of intestinal-location. Conclusions: Rifampicin can activate PXR in humanintestinal biopsies. Biopsies taken from IBD patients have higher NF-κB activity than thebiopsies taken from control patients. Nevertheless, this high NF-κB activity could be reducedby Rifampicin, irrespective of disease type. Thus, PXR activation by Rifampicin could beused as a therapeutic approach to reduce mucosal inflammation in patients with IBD.

Tu1886

The Effect of Infliximab and Adalimumab Treatment on Angiogenic FactorLevels in Patients With Inflammatory Bowel Disease (IBD)Alicia Algaba, Pablo M. Linares, Maria Encarnacion Fernandez Contreras, AriadnaFiguerola, Xavier Calvet, Iván Guerra, José Carlos Villa, Maria Chaparro, José LuisRodríguez Agullo, Javier P. Gisbert, Fernando Bermejo

Aims: Effectiveness of Infliximab (IFX) and Adalimumab (ADA) treatment could be relatedto the modification of different angiogenic proteins (AP), VEGF, PlGF, Ang1 and Ang2 andtheir receptor Tie2. Our aim was to compare the concentrations of these AP in patients withIBD and healthy controls and to analyze their modifications during IFX and ADA treatment.Methods: Prospective and case-control study in healthy controls and patients with IBD thatinitiate treatment with IFX or with ADA. One serum sample from each control was obtained.Four samples were obtained from each IBD patient previous to each of the first 3 doses ofIFX (week 0,2,6) or ADA (week 0,2,4) and at week 14. AP serum concentrations weredetermined by ELISA. Ulcerative colitis (UC) and Crohn disease (CD) activity was ascertainedby CDAI and modified Truelove-Witts indexes, respectively. Clinical response: decrease ofat least five points in the Truelove-modified index, or of at least 70 points of CDAI index.Clinical remission: reduction to a score below 11 points in the modified Truelove-Witts

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sindex, or below 150 points in the CDAI index. Results: 40 controls and 41 patients withIBD that initiate treatment with IFX (19 CD, 6 UC) or with ADA (15 CD, 1 UC) wereincluded. 70% of patients were in concomitant treatment with corticoids and 77% withthiopurines. In 66.7% of cases there was response to IFX/ADA therapy. At week 14, 72%of patients were in clinical remission. No significant differences of AP serum concentrationsbetween patients with IBD and healthy controls were found. Apart from PlGF (p<0.05),concentrations of VEGF, Ang1, Ang2 and Tie2, were unchanged during treatment with IFX/ADA. There were no significant differences between CD and UC, IFX and ADA treatmentor between responders and non-responders to IFX/ADA treatment. Conclusions: PlGF serumlevels and it pro-inflammatory activity seem to be down-regulated by antiTNF therapy.Nevertheless, the effectiveness of IFX and ADA treatment is not be related to modificationsin the concentrations of the other angiogenic factors (VEGF, Ang1, Ang2 and Tie2).

* Significant differences (p<0.05) respect to pre-treatment values.

Tu1887

The Gene Encoding the G Protein-Coupled Receptor 68 (GPR68/ OGR1) isRegulated by TNF, Hypoxia, and Low pH in Human Monocytic CellsCheryl de Valliere, Solange Vidal, Irina Vetter, Marco Inserra, Richard J. Lewis, MatthewA. Cooper, Susanne Bentz, Yu Wang, Marie-Gabrielle Ludwig, Gerd A. Kullak-Ublick,Klaus Seuwen, Carsten A. Wagner, Gerhard Rogler, Jyrki J. Eloranta

Background: The G protein-coupled receptors, ovarian cancer G-protein coupled receptor1 (OGR1/GPR68), GPR4 and T-cell death associated gene 8 (TDAG8/ GPR65) function assensors for extracellular protons, leading to activation of adenylyl cyclase or phospholipaseC. Inflammatory bowel disease (IBD) is associated with acidification of mucosal tissue, andsubsequent proinflammatory cytokine production. The cytokine tumor necrosis factor (TNF)is of crucial importance in IBD pathogenesis, and many of its effects are mediated by thetranscription factor nuclear factor-κB (NF-κB). Furthermore, tissue hypoxia, which stabilizesthe transcription factor hypoxia-inducible factor-1α (HIF-1α), is a feature of active IBD.We studied whether TNF and hypoxia regulate the expression of OGR1 and TDAG8, whichare expressed in both immune cells and colonic tissue. Methods/Results: Treatment of thehuman monocytic cell line MM6 cells with TNF, but none of the other cytokines (IFN-γ,IL-1β, IL-6, TGF-β) tested, led to significant upregulation of OGR1 mRNA, in a dose-dependent manner, as determined by real-time PCR. Macrophagic differentiation of MM6cells with phorbol myristate acetate (PMA) also led to a significant increase in OGR1 mRNAexpression. TNF- and PMA-dependent induction of OGR1 mRNA was confirmed in primaryhuman monocytes. Induction of OGR1 mRNA expression by TNF was reversed by simultan-eous treatment of cells with specific NF-κB inhibitors. In agreement with the findings atthe mRNA level, GPCR activity in MM6 cells was increased upon treatment with TNF orPMA, only at acidic pH, as quantified by intracellular calcium dyes and EPIC label-freeassays. In hypoxia, both 0.2% and 2% oxygen conditions enhanced TNF- and PMA-inductionof OGR1 mRNA expression. Consistent with the hypoxia effect in MM6 cells, OGR1 expres-sion was elevated in colonic tumours in mice. Two alternative predicted promoter variants~9 kpb apart, exist for theOGR1 gene in chromosome 14. In silico analysis usingMatInspectorsoftware and visual inspection revealed several putative DNA-binding sites for NF-κB andHIF-1α within the proximal regions of the OGR1 promoter variants. In addition to TNFand hypoxia, OGR1 mRNA expression was elevated at low pH, suggesting positive feed-forward regulation of OGR1 activity in acidic conditions. No induction of mRNA expressionof the related GPCR, TDAG8, was observed upon treatment with TNF or PMA. Conclusion:OGR1 expression is induced in cells of human macrophage lineage and primary humanmonocytes by TNF and PMA. NF-κB inhibition reverses the induction of OGR1 mRNAexpression by TNF. Interestingly, hypoxia, known to cross-talk with the NF-κB pathway,enhances the TNF-mediated induction of OGR1 expression. The stimulation of OGR1expression by TNF and hypoxia, and subsequently pH-sensing activity, may play a role inIBD pathogenesis.

Tu1888

Protective Role of Sydecan-4 in Experimental ColitisDominik Bettenworth, Athanasios Stratis, Tobias M. Nowacki, Jan Heidemann, PapThomas, Andreas Luegering

Background and Aims: Syndecan (Sdc) proteoglycans are transmembrane proteins withreceptor function and impact on inflammation and wound healing. While cartilage damagewas preserved in Syndecan-4(Sdc4)-deficient mice in a model of osteoarthritis, the impactof Sdc4 on experimental colitis is unclear. The aim of this study was to investigate if theloss of Sdc4 changes the natural course of murine experimental colitis. Methods: ExperimentalColitis was induced in Sdc4-/- mice and in C57BL/6 WT mice (n=5/group) by DSS. Thecourse of colitis was monitored by weight loss as well as assessment of colon length andblinded histological scoring of colonic changes at the end of the experiment. In addition,Sdc4-/- and C57BL/6 WT mice (n=5/group) were orally gavaged with 5×108 colony-formingunits of Citrobacter rodentium (C. rodentium). Fecal excretion of C. rodentium and changesof body weight were monitored. At day 21 post infection, inflammatory changes of thecolon were evaluated histologically. Furthermore, the uptake of Evans Blue into the colonicmucosa of Sdc4-/- and WT mice (n=3/group) was measured In Vivo to evaluate the intestinalbarrier function. Results: After induction of colitis, both groups lost body weight. Beginningfrom day 5 after start of DSS-administration, sdc4-/- mice lost dramatically more body weight

S-870AGA Abstracts

compared to WT animals (day 8: 24.8% ± 1.9 vs. 9.2% ± 3.1; p=0.008). In accordancewith the increased loss of body weight, the colon length of sdc4-/- mice was significantlyshortened (63.3 mm ± 2.4 vs. 74.8 ± 2.3; p=0.01) and the histological damage accordingto the Dieleman-Score was markedly aggravated (16AU ± 3.7 vs. 3.4AU ± 0.2; p=0.016).At day 19 post infection, the fecal excretion of C. rodentium in sdc4-/- mice was increasedup to 2 log10 compared to WT animals (2.5x105 ± 6.8x103 vs. 9.6x103 ± 6.5x102; p=0.01).Histological damage of colonic mucosa, reflected by lengthening of crypts, was increasedin Sdc4-/- mice (14.3AU ± 1.3 vs. 10.2AU ± 0.9; p=0.03). The colonic uptake of Evans Bluein Sdc4-/- mice was not altered compared to healthy WT mice (0.34 extinction/gram colontissue ± 0.03 vs. 0.39 extinction/gram colon tissue ± 0.07) indicating that the intestinalbarrier function of Sdc4-/- mice is not per se impaired. Conclusions: Syndecan-4 may exertprotective effects in intestinal inflammation. Future studies are needed to explore potentialtherapeutic effects of Syndecan-4 in inflammatory bowel disease.

Tu1889

Evidence of Functional Cross-Talk Between the Notch and NF-kB Pathways inNon-Neoplastic Hyperproliferating Colonic EpitheliumIshfaq Ahmed, Parthasarathy Chandrakesan, Lijun Xia, Shrikant Anant, Shahid Umar

Background: Notch and NF-κB pathways are key regulators of numerous cellular eventssuch as proliferation, differentiation, or apoptosis. However, the cross-talk between Notchand NF-κB is a biological Pandora's Box that has just been opened. Aim: To examinefunctional cross-talk between the Notch and NF-κB pathways during bacterial infection-induced hyperplasia and/or inflammation in the colon. Methods: Transmissible murinecolonic hyperplasia (TMCH) was induced by Citrobacter rodentium (CR) infection. Coloniccrypts or crypt-denuded lamina propria (CLP) were separated and standard molecular andbiochemical techniques were employed. Results: During TMCH, relative levels of Notchintracellular domain increased significantly in the crypts of NIH:Swiss outbred mice alongwith upregulation of Jagged-1 and Hes-1 coinciding with progression (days 6-12) andregression (days 20-34) phases of hyperplasia. Changes in NF-κB activity and subunitphosphorylation including increases in downstream target CXCL-1/KC expression paralleledsignaling via components of the Notch pathway at these time points. Blocking Notch signalingacutely for 5-days with Notch blocker dibenzazepine (DBZ @ 10μmol/Kg body wt) before(days 0-3) or after (days 3-6) the onset of hyperplasia, failed to inhibit crypt NF-κB activityor CXCL-1/KC expression. Chronic DBZ administration for 10-days starting 2-days post-infection followed by euthanasia at day-12 blocked both Notch and NF-κB signaling in thecrypts resulting in abrogation of hyperplasia. Interestingly, we discovered significant colitisin NIH:Swiss mice receiving CR/DBZ compared to CR alone concomitant with disruptionof the mucinous gel layer encompassing the intestinal barrier. Even more intriguing wasexacerbation of colitis in response to CR/DBZ in mice lacking Core3-derived O-glycans, theprimary component of the intestinal mucins. The colitis in these mice was apparentlymediated by NF-κB-dependent increases in IL-1α, G-CSF, MIP-1β, MCP-1, MIP-2 and KCeither in whole distal colon or in the CLP that facilitated recruitment of neutrophils to thesubepithelial regions leading to increases in myeloperoxidase activity. Dietary Bael (Aeglemarmelos) extract (4%) and curcumin (4%) restored Notch and NF-κB signaling and inhib-ited CR/DBZ-induced apoptosis in the crypts thereby promoting crypt regeneration andamelioration of colitis. Conclusions: 1. Functional cross-talk exists between the Notch andNF-κB pathways during TMCH. 2. Blocking NF-κB activity in the colonic crypts alone isnot sufficient to ameliorate inflammation and/or colitis mediated probably by sustained NF-κB activation in the CLP. Significance: Development of small molecule inhibitors that targetstromal NF-κB and not necessarily the Notch blockers, will be a better therapeutic strategyto mitigate inflammation and/or colitis following bacterial infection.

Tu1890

Prostaglandin E2 Opposes IL-23 Plus IL-1β in the Induction of the TH1Immune Response and Instead Promotes an IL-17A Predominant TH17/TH2Immune ResponseArthur Barrie, Matthew Henkel, Regan Scott, Martha Porter, Yingze Zhang, John Kloke,Anuradha Ray, Richard H. Duerr

Background: Inflammatory bowel disease (IBD) is propagated by interleukin (IL-17) produ-cing CD4+ T helper (Th17) cells, which are induced and modulated by interleukin (IL)-23, IL-1beta(β), and prostaglandin E2 (PGE2). Prior studies investigating human effectormemory T cell gene expression traits in response to IL-23, IL-1β and PGE2 have beenlimited. We sought to define the expression profiles of human CD4+ effector memory Tcells after stimulation through the T cell receptor and costimulatory molecules alone or incombination with IL-23 plus IL-1β, and/or PGE2. Methods: We characterized the geneexpression of human CD4+ effector memory T cells from 14 blood donors in response to6 hours of treatment with anti-CD2/CD3/CD28 antibodies alone or in combination withIL-23 plus IL-1β, and/or PGE2 using a real-time quantitative polymerase chain reaction(PCR) array. To verify our gene expression findings, we measured related protein productionof 9 additional blood donors using multiplex and individual enzyme-linked immunosorbentassay (ELISA) analysis. Results: We show for the first time that IL-23 plus IL-1β and PGE2synergistically induce the expression of IL-8 and IL-9 and confirm previous reports of theirsynergistic effects on IL-17A expression. In contrast, we discovered that IL-23 plus IL-1βand PGE2 differentially regulate the expression of IL-17F, IL-22 and IL-6, which are repressedby PGE2 but induced and dominated by IL-23 plus IL-1β. IL-23 plus IL-1β alone preferen-tially enhance IL-17F expression, but the addition of PGE2 only enhances IL-17A expressionand thus promotes a switch from an IL-17F to an IL-17A predominant immune response.PGE2 simultaneously induces IL-5 and IL-13 while repressing the IL-23 plus IL-1β-mediatedinduction of granulocyte-macrophage colony-stimulating factor (GM-CSF), interferon-gamma (IFN-γ), and tumor necrosis factor-alpha (TNF-α), and the gene expression of IL21and IL23R. Conclusions: Our study demonstrates that PGE2 opposes IL-23 plus IL-1β inthe induction of the Th1 immune response and instead promotes an IL-17A predominantTh17/Th2 immune response that potentially favors neutrophil migration and host protectionrather than chronic inflammation and autoimmunity.