Cytokine production by dendritic cells genetically engineered to express IL-4: induction of Th2 responses and differential regulation of IL-12 and IL-23 synthesis

Characterization and Activation of Fas Ligand-Producing Mouse B Cells and Their Killer Exosomes

B lymphocytes make several contributions to immune regulation including production of antibodies with regulatory properties, release of immune suppressive cytokines, and expression of death-inducing ligands. A role for Fas ligand (FasL)-expressing "killer" B cells in regulating T helper (T_H) cell survival and chronic inflammation has been demonstrated in animal models of schistosome worm and other infections, asthma, autoimmune arthritis, and type 1 diabetes. FasL⁺ B cells were also capable of inducing immune tolerance in a male-to-female transplantation model. Interestingly, populations of B cells found in the spleen and lungs of naïve mice constitutively expresses FasL and have potent killer function against T_H cells that is antigen-specific and FasL-dependent. Epstein-Barr virus-transformed human B cells constitutively express FasL and package it into exosomes that co-express MHC Class II molecules and have killer function against antigen-specific T_H cells. FasL⁺ exosomes with markers of B-cell lineage are abundant in the spleen of naïve mice. Killer B cells therefore represent a novel target for immune modulation in many disease settings. Our laboratory has published methods of characterizing FasL⁺ B cells and inducing their proliferation in vitro. This updated chapter will describe methods of identifying and expanding killer B cells from mice, detecting FasL expression in B cells, extracting FasL⁺ exosomes from spleen and culture supernatants, and performing functional killing assays against antigen-specific T_H cells.

Differential Influence on Regulatory B Cells by TH2 Cytokines Affects Protection in Allergic Airway Disease

The role of regulatory B cells (Bregs) in modulating immune responses and maintaining tolerance are well established. However, how cytokines present during immune responses affect Breg growth and function are not as well defined. Previously, our laboratory reported IL-5- and mCD40L-expressing fibroblast (mCD40L-Fb) stimulation induced IL-10 production from murine B cells. The current study investigated the phenotype and functional relevance of IL-10- producing B cells from this culture. We found IL-5/mCD40L-Fb stimulation induced IL-10 production exclusively from CD5⁺ splenic B cells of naive mice. After stimulation, the resulting IL-10⁺ B cells displayed markers of multiple reported Breg phenotypes. Interestingly, when investigating effects of IL-4 (a critical T_H2 cytokine) on IL-5/mCD40L-Fb-induced IL-10 production, we found IL-4 inhibited IL-10 production in a STAT6-dependent manner. Upon adoptive transfer, CD5⁺ B cells previously stimulated with IL-5/mCD40L-Fb were able to reduce development of OVA-induced allergic airway disease in mice. Using B cells from IL-10 mutant mice differentiated by IL-5/mCD40L-Fb, we found protection from allergic airway disease development was dependent on the IL-10 production from the transferred B cells. Bregs have been shown to play crucial roles in the immune tolerance network, and understanding stimuli that modulate their growth and function may be key in development of future treatments for diseases of immune dysregulation.

Characterization and activity of Fas ligand producing CD5⁺ B cells

B lymphocytes make several contributions to immune regulation including production of antibodies with regulatory properties, release of immune suppressive cytokines, and expression of death-inducing ligands. A role for Fas ligand (FasL)-expressing "killer" B cells in regulating T helper cell survival and chronic inflammation has been demonstrated in animal models of schistosome worm infection, asthma, and autoimmune arthritis. Interestingly, a population of CD5(+) B cells found in the spleen and lungs of naïve mice constitutively expresses FasL and has potent killer function against T helper cells that is antigen-specific and FasL-dependent. Killer B cells therefore represent a novel target for immune modulation in many disease settings. Our laboratory has recently published methods of characterizing FasL(+) B cells and inducing their proliferation in vitro. This chapter will describe detailed methods of identifying and expanding killer B cells from mice, detecting FasL expression in B cells, and performing functional killing assays against antigen-specific TH cells.

IL-4 abrogates T(H)17 cell-mediated inflammation by selective silencing of IL-23 in antigen-presenting cells

Interleukin 4 (IL-4) can suppress delayed-type hypersensitivity reactions (DTHRs), including organ-specific autoimmune diseases in mice and humans. Despite the broadly documented antiinflammatory effect of IL-4, the underlying mode of action remains incompletely understood, as IL-4 also promotes IL-12 production by dendritic cells (DCs) and IFN-γ-producing T(H)1 cells in vivo. Studying the impact of IL-4 on the polarization of human and mouse DCs, we found that IL-4 exerts opposing effects on the production of either IL-12 or IL-23. While promoting IL-12-producing capacity of DCs, IL-4 completely abrogates IL-23. Bone marrow chimeras proved that IL-4-mediated suppression of DTHRs relies on the signal transducer and activator of transcription 6 (STAT6)-dependent abrogation of IL-23 in antigen-presenting cells. Moreover, IL-4 therapy attenuated DTHRs by STAT6- and activating transcription factor 3 (ATF3)-dependent suppression of the IL-23/T(H)17 responses despite simultaneous enhancement of IL-12/TH1 responses. As IL-4 therapy also improves psoriasis in humans and suppresses IL-23/T(H)17 responses without blocking IL-12/T(H)1, selective IL-4-mediated IL-23/T(H)17 silencing is promising as treatment against harmful inflammation, while sparing the IL-12-dependent T(H)1 responses.

Interleukin-5 supports the expansion of fas ligand-expressing killer B cells that induce antigen-specific apoptosis of CD4(+) T cells and secrete interleukin-10

Beyond their critical role in humoral immunity, B lymphocytes can employ a variety of immunomodulatory mechanisms including expression of the apoptosis-inducing molecule Fas ligand (FasL; CD178). Here, we extensively characterized the surface phenotype of FasL⁺ killer B cells, showing they are enriched in the IgM^highCD5⁺CD1d^high B cell subset previously reported to contain a higher frequency of B cells producing interleukin-10 (IL-10). A rare population of B cells expressing IL-10 was present among FasL⁺ B cells, but most FasL⁺ B cells did not produce IL-10. We also identify interleukin-5 (IL-5) as a novel inducer of killer B cell function. Constitutively FasL⁺ B cells expressed higher levels of the IL-5 receptor, and treating B cells with IL-5 and CD40L resulted in the expansion of a B cell population enriched for FasL⁺ cells. B cells stimulated with IL-5 and CD40L were potent inducers of apoptosis in activated primary CD4⁺ T cells, and this killing function was antigen-specific and dependent upon FasL. IL-5 also enhanced IL-10 secretion in B cells stimulated with CD40L. Taken together these findings elucidate the relationship of FasL⁺ B cells and IL-10-producing B cells and demonstrate that IL-5 can induce or enhance both killer B cell activity and IL-10 secretion in B cells. Finally, we found that the killer B cell activity induced by IL-5 was completely blocked by IL-4, suggesting the existence of a previously unknown antagonistic relationship between these type-2 cytokines in modulating the activity of killer B cells. Targeting this IL-5/IL-4 signaling axis may therefore represent a novel area of drug discovery in inflammatory disorders.

An overview of cytokine interactions in atherosclerosis and implications for peripheral arterial disease

Over the last three decades, a surge in research into the inflammatory pathophysiology of atherosclerosis has highlighted an array of cytokines and other inflammatory mediators associated with underlying inflammatory burden. The ability to identify and simultaneously measure multiple cytokines in peripheral blood highlights their potential as biomarkers of atherosclerosis. This has prompted much research in vascular medicine to identify the ;at-risk' groups for atherostenotic or atheroaneurysmal disease. This review is compiled with similar intentions and aims to discern the relevant evidence for cytokine profiling in peripheral arterial disease (PAD), where such information is lacking, while providing a holistic overview of cytokine interactions in atherosclerosis. This is pertinent given that cytokine profiles from coronary artery disease and aortic aneurysm studies cannot be directly extrapolated to PAD due to differences in inflammatory environments that exist in these conditions. Whilst plaque morphology and blood rheology play an important role in the cardiac manifestations of atherosclerosis, tissue thrombogenecity is very important in PAD. Further, cytokines act in concert rather than in isolation in a disease process, and no single cytokine in a cross-sectional model is able to serve as an absolute screening marker. Thus, it is essential to understand the regulation of cytokine production in atherosclerosis prior to evaluating the viability and merits of a multimarker approach for clinical risk stratification in PAD.

Interleukin-12 but not interleukin-18 is associated with severe endometriosis

OBJECTIVE

To evaluate interleukin (IL)-12 and IL-18 levels in the serum and peritoneal fluid of women with and without endometriosis.

DESIGN

Cross-sectional survey.

SETTING

University hospital.

PATIENTS

Interleukin-12 and IL-18 levels were compared in 105 patients submitted to laparoscopy because of symptoms suggestive of endometriosis (pain and/or infertility). The disease was confirmed in 72 patients (study group), while in 33 patients findings were not compatible with endometriosis (control group). INTEVENTION(S): Blood sample and peritoneal fluid were obtained from patients during videolaparoscopy.

MAIN OUTCOME MEASURE(S)

The levels of IL-12 and IL-18 in peripheral blood and peritoneal fluid were determined and compared with the stage and site of the disease and histologic classification.

RESULT(S)

IL-12 levels measured in peritoneal fluid were higher in patients with endometriosis compared with the control group. A significant increase in IL-12 levels was found when the more advanced stages of the disease were compared with the initial stages. No statistically significant differences were found in IL-18 levels, either in serum or in peritoneal fluid samples.

CONCLUSION(S)

Patients with severe endometriosis have higher IL-12 levels irrespective of IL-18 levels, suggesting that in this disease an alternative pathway is involved in induction of the Th1 immune response.

The role of T cells in rheumatoid arthritis: new subsets and new targets

PURPOSE OF REVIEW

To update the knowledge on the contribution of T cells in rheumatoid arthritis, a selection of publications between the end of 2005 and 2006 were reviewed.

RECENT FINDINGS

Th17 cells driven by TGF-beta, IL-1, IL-6 and IL-23 challenge previous concepts of 'Th1'-induced rheumatoid arthritis. Other advancements in IL-17 studies include novel concepts on the IL-17 receptor and additional information on the mechanism of IL-17-induced effects. Regulatory T cells fail to control disease due to defective function secondary to the synovial inflammatory milieu. The predominance of pathogenic effector T cells in the presence of impaired T-cell regulatory mechanisms may therefore contribute to rheumatoid arthritis chronicity. Cellular therapies attempt to restore the balance that includes production of immunoregulatory cytokines such as IL-4 or IL-10. Better T-cell-targeted therapies controlling costimulation are in place with purported increased efficacy and durability, including anti-tumour necrosis factor nonresponders. Additional direct and indirect T-cell approaches include antagonism of T-cell-derived cytokines, T-cell activation or B-cell ablation.

SUMMARY

A renewed interest in T cells comes from the discovery of Th17 in rheumatoid arthritis and from novel findings on the role of T cells in rheumatoid arthritis induction, chronicity and relapse.

Fluvastatin reverses endothelial dysfunction and increased vascular oxidative stress in rat adjuvant-induced arthritis

OBJECTIVE

To investigate the effect of statins on vascular dysfunction in rat adjuvant-induced arthritis (AIA).

METHODS

Fluvastatin (5 mg/kg/day) was administered orally to rats with AIA, for 21 days after the onset of arthritis. The vasodilatory response to acetylcholine of aortic rings isolated from rats with AIA that were not treated or were treated with fluvastatin and from normal rats was determined. The amounts of 4-hydroxy-2-nonenal (HNE) and nitrotyrosine in aortas were measured by Western blotting. In vitro and in situ superoxide production in aortas was evaluated based on fluorogenic oxidation of dihydroethidium to ethidium. Expression of NAD(P)H components and endothelial nitric oxide synthase (eNOS) in aortas was examined by real-time reverse transcriptase-polymerase chain reaction and Western blotting. Serum levels of tetrahydrobiopterin, a critical eNOS cofactor, were determined by high-performance liquid chromatography.

RESULTS

Fluvastatin reversed endothelial dysfunction in AIA without affecting the clinical severity of arthritis or serum cholesterol concentration. Fluvastatin reduced the amounts of HNE and nitrotyrosine in the aorta, and the levels of superoxide expressed in endothelial cells and smooth muscle cells in the tissue, in rats with AIA. NADH- or L-arginine-induced superoxide production was not observed in the aortic samples from fluvastatin-treated rats with AIA. Fluvastatin decreased the levels of expression of messenger RNA for p22phox, a NAD(P)H oxidase component, in the aortas of rats with AIA, but did not affect the expression of eNOS. Serum levels of tetrahydrobiopterin were significantly reduced in rats with AIA, and were increased by administration of fluvastatin.

CONCLUSION

Our findings demonstrate that fluvastatin has potent vascular protective effects in AIA and provide additional scientific rationale for the use of statins to reduce cardiovascular mortality in patients with rheumatoid arthritis.

Interleukin-17 as a molecular target in immune-mediated arthritis: immunoregulatory properties of genetically modified murine dendritic cells that secrete interleukin-4

OBJECTIVE

Our previous studies have shown that murine dendritic cells (DCs) genetically modified to express interleukin-4 (IL-4) reduce the incidence and severity of murine collagen-induced arthritis. The present studies were performed to assess the immunoregulatory mechanisms underlying this response, by assessing the effects of IL-4 DCs on cytokine production by subsets of T helper cells.

METHODS

Male DBA mice ages 6-8 weeks old were immunized with type II collagen. Splenic T cells obtained during the initiation phase and the end stage of arthritis were cultured with IL-4 DCs or untransduced DCs in the presence of collagen rechallenge. Interferon-gamma (IFNgamma) and IL-17 responses were measured. Antibodies to IL-4, IL-12, and IL-23, and recombinant IL-4, IL-12, and IL-23 were used to further study the regulation of T cell cytokine production by IL-4 DCs.

RESULTS

Splenic T cells obtained during the initiation phase of arthritis produced less IL-17 when cultured in the presence of IL-4 DCs, despite their production of increased quantities of other proinflammatory cytokines (IFNgamma and tumor necrosis factor). T cell IL-17 production after collagen rechallenge was not inhibited by a lack of IL-23, since IL-4-mediated suppression of IL-17 was not reconstituted by IL-23, an otherwise potent inducer of IL-17 production by T cells. Although IL-4 DCs can produce increased quantities of IL-12 and IFNgamma, suppression of IL-17 production by IL-4 DCs was independent of both. While IL-17 production by T cells obtained during the initiation phase of arthritis was regulated by IL-4 DCs, IL-17 production by T cells obtained during end-stage arthritis was not altered.

CONCLUSION

Our data suggest that IL-4 DCs exert a therapeutic effect on collagen-induced arthritis by targeting IL-17. IL-17 suppression by IL-4 DCs is robust and is not reversed by IL-23. Timing might be important in IL-17-targeted therapy, since IL-17 production by T cells obtained during end-stage arthritis did not respond to suppression by IL-4 DCs.

Endothelial dysfunction in rat adjuvant-induced arthritis: vascular superoxide production by NAD(P)H oxidase and uncoupled endothelial nitric oxide synthase

OBJECTIVE

To investigate endothelial function and levels of vascular oxidative stress in rat adjuvant-induced arthritis (AIA), in view of mounting evidence for an association between rheumatoid arthritis (RA) and accelerated vascular disease.

METHODS

Thoracic aortic rings were prepared from AIA and control rats. After preconstriction by norepinephrine, the vasodilatory response to acetylcholine was determined. The amounts of 4-hydroxy-2-nonenal (HNE) and nitrotyrosine in AIA rat aortas were measured by Western blotting. Homogenates of the aortas were incubated with various substrates for superoxide-producing enzymes, and superoxide production was assessed by fluorogenic oxidation of dihydroethidium to ethidium. Expression of endothelial nitric oxide synthase (eNOS) in aortas was examined by real-time reverse transcriptase-polymerase chain reaction and Western blotting. Serum levels of tetrahydrobiopterin (BH4), a critical eNOS cofactor, were determined by high-performance liquid chromatography.

RESULTS

Endothelium-dependent relaxation of the aortic ring was significantly depressed in AIA rats compared with control rats. The amounts of HNE and nitrotyrosine were increased in AIA rat aortas, indicating overproduction of reactive oxygen species. Incubation of AIA rat aorta homogenates with NADH or L-arginine, a substrate of eNOS, resulted in a significant increase in superoxide production. Endothelial NOS was highly expressed in AIA rat aortas. Serum levels of BH4 were significantly lower in AIA. Treatment of AIA with BH4 reversed the endothelial dysfunction, suggesting that its deficiency may contribute to the uncoupling of eNOS.

CONCLUSION

Vascular dysfunction in RA can be partially modeled in animals. NAD(P)H oxidase and uncoupled eNOS are responsible for the increase in vascular oxidative stress, which is likely to be involved in the endothelial dysfunction in AIA.

Interleukin-4 can induce interleukin-4 production in dendritic cells

The presence of interleukin-4 (IL-4) during the generation of dendritic cells (DC) from precursor cells results in measurable increases of IL-12 in supernatants but IL-4 secretion has not been reported. However, DC have IL-4 receptors and are able to make IL-4. We therefore sought evidence for autocrine effects of IL-4 on DC. IL-4 gene expression was low in DC generated from bone-marrow stem cells in the presence of granulocyte-macrophage colony-stimulating factor but was up-regulated by exposure of the developing DC to IL-4. Exposure to IL-4 also induced intracellular IL-4 production in DC. The intracellular IL-4 induced in the presence of IL-4 was increased following further DC maturation with tumour necrosis factor-alpha. By contrast, in supernatants of DC, IL-4 was rarely detected and only at late culture periods. However, after exposure of DC to IL-4, cell-bound IL-4 was detected transiently, which suggested binding and internalization of the cytokine. Binding via IL-4 receptor-alpha was indicated from phosphorylation of the signal transducer and activator of transcription (STAT) protein 6, which is known to mediate IL-4 function. Cytokine persisting within the supernatants of the cells may therefore be unrepresentative of the actual production and function of IL-4 in the cells; IL-4 may be produced in DC in response to exposure to IL-4 but may then be lost from the supernatants during cell binding and activation of the cells.