Macrophages, but not dendritic cells, present collagen to T cells

Paradoxical Duel Role of Collagen in Rheumatoid Arthritis: Cause of Inflammation and Treatment

In biology, collagen-biomaterial regulates several signaling mechanisms of bone and immune cells involved in tissue repair and any imbalance in collagen turnover may affect the homeostasis of cells, becoming a major cause of several complications. In this case, the administration of oral collagen may play a potential role in returning cells to their normal function. For several decades, the beneficial effects of collagen have been explored widely, and thus many commercial products are available in cosmetics, food, and biomedical fields. For instance, collagen-based-products have been widely used to treat the complications of cartilage-related-disorders. Many researchers are reporting the anti-arthritogenic properties of collagen-based materials. In contrast, collagen, especially type-II collagen (CII), has been widely used to induce arthritis by immunization in an animal-model with or without adjuvants, and the potentially immunogenic-properties of collagen have been continuously reported for a long time. Additionally, the immune tolerance of collagen is mainly regulated by the T-lymphocytes and B-cells. This controversial hypothesis is getting more and more evidence nowadays from both sides to support its mechanism. Therefore, this review links the gap between the arthritogenic and anti-arthritogenic effects of collagen and explored the actual mechanism to understand the fundamental concept of collagen in arthritis. Accordingly, this review opens-up several unrevealed scientific knots of collagen and arthritis and helps the researchers understand the potential use of collagen in therapeutic applications.

Antiinflammatory Medicinal Plants from the Ugandan Greater Mpigi Region Act as Potent Inhibitors in the COX-2/PGH2 Pathway

Our study investigates 16 medicinal plants via assessment of inhibition of proinflammatory enzymes such as cyclooxygenases (COX). The plants are used by traditional healers in the Greater Mpigi region in Uganda to treat inflammation and related disorders. We present results of diverse in vitro experiments performed with 76 different plant extracts, namely, (1) selective COX-2 and COX-1 inhibitor screening; (2) 15-LOX inhibition screening; (3) antibacterial resazurin assay against multidrug-resistant Staphylococcus aureus, Listeria innocua, Listeria monocytogenes, and Escherichia coli K12; (4) DPPH assay for antioxidant activity; and (5) determination of the total phenolic content (TPC). Results showed a high correlation between traditional use and pharmacological activity, e.g., extracts of 15 out of the 16 plant species displayed significant selective COX-2 inhibition activity in the PGH₂ pathway. The most active COX-2 inhibitors (IC₅₀ < 20 µg/mL) were nine extracts from Leucas calostachys, Solanum aculeastrum, Sesamum calycinum subsp. angustifolium, Plectranthus hadiensis, Morella kandtiana, Zanthoxylum chalybeum, and Warburgia ugandensis. There was no counteractivity between COX-2 and 15-LOX inhibition in these nine extracts. The ethyl acetate extract of Leucas calostachys showed the lowest IC₅₀ value with 0.66 µg/mL (COX-2), as well as the most promising selectivity ratio with 0.1 (COX-2/COX-1). The TPCs and the EC₅₀ values for DPPH radical scavenging activity showed no correlation with COX-2 inhibitory activity. This led to the assumption that the mechanisms of action are most likely not based on scavenging of reactive oxygen species and antioxidant activities. The diethyl ether extract of Harungana madagascariensis stem bark displayed the highest growth inhibition activity against S. aureus (MIC value: 13 µg/mL), L. innocua (MIC value: 40 µg/mL), and L. monocytogenes (MIC value: 150 µg/mL). This study provides further evidence for the therapeutic use of the previously identified plants used medicinally in the Greater Mpigi region.

Extracellular traps and PAD4 released by macrophages induce citrullination and auto-antibody production in autoimmune arthritis

The mechanisms underlying the transition of rheumatoid arthritis (RA) systemic autoimmunity to the joints remain largely unknown. Here, we demonstrate that macrophages in the secondary lymphoid organs (SLOs) and synovial ectopic lymphoid-like structures (ELSs) express peptidylarginine deiminase 4 (PAD4) in murine collagen induced arthritis (CIA) and synovial biopsies from RA patients. Moreover, peptidyl citrulline colocalized with macrophages in SLOs and ELSs, and depletion of macrophages in CIA decreased lymphoid tissue citrullination and serum anti-citrullinated protein/peptide antibody (ACPA) levels. Furthermore, PAD was released from activated murine and RA synovial tissue and fluid (SF) macrophages which functionally deiminated extracellular proteins/peptides in vitro. Additionally, activated murine and SF macrophages displayed macrophage extracellular trap formation (METosis) and release of intracellular citrullinated histones. Moreover, presentation of citrullinated proteins induced ACPA production in vitro. Thus, lymphoid tissue macrophages contribute to self-antigen citrullination and ACPA production, indicating that their selective targeting would potentially ameliorate citrullination-dependent autoimmune disorders.

Comparative and network-based proteomic analysis of low dose ethanol- and lipopolysaccharide-induced macrophages

Macrophages are specialized phagocytes that play an essential role in inflammation, immunity, and tissue repair. Profiling the global proteomic response of macrophages to microbial molecules such as bacterial lipopolysaccharide is key to understanding fundamental mechanisms of inflammatory disease. Ethanol is a widely abused substance that has complex effects on inflammation. Reports have indicated that ethanol can activate or inhibit the lipopolysaccharide receptor, Toll-like Receptor 4, in different settings, with important consequences for liver and neurologic inflammation, but the underlying mechanisms are poorly understood. To profile the sequential effect of low dose ethanol and lipopolysaccharide on macrophages, a gel-free proteomic technique was applied to RAW 264.7 macrophages. Five hundred four differentially expressed proteins were identified and quantified with high confidence using ≥ 5 peptide spectral matches. Among these, 319 proteins were shared across all treatment conditions, and 69 proteins were exclusively identified in ethanol-treated or lipopolysaccharide-stimulated cells. The interactive impact of ethanol and lipopolysaccharide on the macrophage proteome was evaluated using bioinformatics tools, enabling identification of differentially responsive proteins, protein interaction networks, disease- and function-based networks, canonical pathways, and upstream regulators. Five candidate protein coding genes (PGM2, ISYNA1, PARP1, and PSAP) were further validated by qRT-PCR that mostly related to glucose metabolism and fatty acid synthesis pathways. Taken together, this study describes for the first time at a systems level the interaction between ethanol and lipopolysaccharide in the proteomic programming of macrophages, and offers new mechanistic insights into the biology that may underlie the impact of ethanol on infectious and inflammatory disease in humans.

Syk-Mediated Suppression of Inflammatory Responses by Cordyceps bassiana

The fruit body of artificially cultivated Cordyceps bassiana has been reported to exhibit anti-inflammatory and anticancer activities. Although it has been suggested that the fruit body has neutraceutic and pharmaceutic biomaterial potential, the exact anti-inflammatory molecular mechanism has not been fully elucidated. In this study, we demonstrated the immunopharmacologic activity of Cordyceps bassiana under in vitro conditions and investigated its anti-inflammatory mechanism. Water extract (Cm-WE) of the fruit body of artificially cultivated Cordyceps bassiana without polysaccharide fractions reduced the expression of the proinflammatory genes cyclooxygenase (COX)-2, interleukin (IL)-12, and inducible nitric oxide synthase (iNOS) and promoted the expression of the anti-inflammatory gene IL-10 in lipopolysaccharide (LPS)-treated RAW264.7 cells. In addition, this fraction suppressed proliferation and interferon (IFN)-[Formula: see text] production in splenic T lymphocytes. Cm-WE blocked the activation of nuclear factor (NF)-[Formula: see text]B and activator protein (AP)-1 and their upstream inflammatory signaling cascades, including Syk, MEK, and JNK. Using kinase assays, Syk was identified as the target enzyme most strongly inhibited by Cm-WE. These results strongly suggest that Cm-WE suppresses inflammatory responses by inhibiting Syk kinase activity, with potential implications for novel neutraceutic and pharmaceutic biomaterials.

Blocking of urotensin receptors as new target for treatment of carrageenan induced inflammation in rats

This study investigated possible role of U-II and its receptor expression in inflammation by using UTR agonist and antagonist in carrageenan induced acute inflammation. Rats were divided into 5 groups as (1) Healthy control, (2) Carrageenan control, (3) Carrageenan +Indomethacin 20mg/kg, orally, (4) Carrageenan +AC7954 (U-II receptor agonist, intraperitoneally) 30mg/kg and (5) Carrageenan +SB657510 (UTR antagonist, intraperitoneally) 30mg/kg. 1h after drug administration, carrageenan was injected. At the 3rd hour after carrageenan injection, agonist produced no effect while antagonist 63% anti-inflammatory effect respectively. UTR and UT-II expression increased in carrageenan induced paw tissue. Antagonist administration prevented the decrease in an antioxidant system and also capable to decrease TNF-α and IL-6 mRNA expressions. This study showed the role of urotensin II receptors in the physiopathogenesis of acute inflammatory response that underlying many diseases accompanied by inflammation.

Anti-inflammatory effects of Polygonum minus (Huds) extract (Lineminus™) in in-vitro enzyme assays and carrageenan induced paw edema

Background

The study was aimed to evaluate the anti-inflammatory activity of ethanolic and aqueous extracts of Polygonum minus (Huds) using in vitro and in vivo approaches.

Methods

The in vitro tests used to evaluate ethanolic extract are cyclooxygenase-1 (COX-1), cyclooxygenase-2 (COX-2), lipooxygenase (5-LOX), secretory phospholipase-A2 (sPLA2) inhibition assay whilst the in-vivo effect was measured by the ability of aqueous extracts to reduce paw edema induced by λ-carrageenan, in rats.

Results

The ethanolic extract inhibited the activities of 5-LOX and COX-1(p < 0.05) whilst the inhibitory effect on COX-2 was only moderate. A marked inhibition of 5-LOX was observed at 30 μg/ ml. The extract did not inhibit the activity of sPLA2. The ability of the ethanolic extracts of Polygonum minus to inhibit both 5-LOX and COX, prompted a study to evaluate the effects of using an aqueous extract of Polygonum minus(Lineminus^TM); as this would be more suitable for future clinical testing. The anti-inhibitory activity of the aqueous extract from this plant was evaluated using a rat model where inflammation was induced in the paws by injection of λ-carrageenan. The aqueous extracts from Polygonum minus administered at doses of 100 and 300 mg/kg body weight (b.w.), significantly (p < 0.01) reduced paw edema induced by λ-carrageenan in the experimental model, at 4 h compared to the vehicle control. Furthermore, administration of 100 mg/kg b.w. or 300 mg/kg b.w. completely reduced inflammation of the paw 4 h after injection.

Conclusion

These findings suggest that aqueous extract of Polygonum minus possesses potent anti-inflammatory activities.

IKK β -Targeted Anti-Inflammatory Activities of a Butanol Fraction of Artificially Cultivated Cordyceps pruinosa Fruit Bodies

The inhibitory activities of the Cordyceps pruinosa butanol fraction (Cp-BF) were investigated by determining inflammatory responses of lipopolysaccharide (LPS)-treated RAW264.7 macrophage cells and by evaluating HCl/ethanol (EtOH)-triggered gastric ulcers in mice. The molecular mechanisms of the inhibitory effects of Cp-BF were investigated by identifying target enzymes using biochemical and molecular biological approaches. Cp-BF strongly inhibited the production of NO and TNF-α, release of reactive oxygen species (ROS), phagocytic uptake of FITC-dextran, and mRNA expression levels of interleukin (IL)-6, inducible NO synthase (iNOS), and tumour necrosis factor-alpha (TNF)-α in activated RAW264.7 cells. Cp-BF also strongly downregulated the NF-κB pathway by suppressing IKKβ according to luciferase reporter assays and immunoblot analysis. Furthermore, Cp-BF blocked both increased levels of NF-κB-mediated luciferase activities and phosphorylation of p65/p50 observed by IKKβ overexpression. Finally, orally administered Cp-BF was found to attenuate gastric ulcer and block the phosphorylation of IκBα induced by HCl/EtOH. Therefore, these results suggest that the anti-inflammatory activity of Cp-BF may be mediated by suppression of IKKα and its downstream NF-κB activation. Since our group has established the mass cultivation conditions by developing culture conditions for Cordyceps pruinosa, the information presented in this study may be useful for developing new anti-inflammatory agents.

Myrsine seguinii ethanolic extract and its active component quercetin inhibit macrophage activation and peritonitis induced by LPS by targeting to Syk/Src/IRAK-1

ETHNOPHARMACOLOGICAL RELEVANCE

Myrsine seguinii H. LÉVEILLÉ (syn. Rapanea neriifolia) (Myrsinaceae) is a medicinal plants traditionally used in Myanmar to treat infectious and inflammatory diseases. Since none of reports have systematically demonstrated the anti-inflammatory activity of this plant, we aimed to mechanistically understand the regulatory roles of the plant in inflammatory responses using the ethanolic extract of Myrsine seguinii (Ms-EE).

MATERIALS AND METHODS

Activated macrophages and peritonitis symptoms induced by lipopolysaccharide (LPS) were employed. HPLC analysis was used to identify active components. To characterize direct target enzymes, kinase assay was established.

RESULTS

Ms-EE inhibited the production of nitric oxide (NO) and prostaglandin (PG)E2 in RAW264.7 cells and peritoneal macrophages stimulated by LPS. This extract suppressed the mRNA expression of the inducible NO synthase (iNOS) and cyclooxygenase (COX)-2 genes by down-regulating the activation of nuclear factor (NF)-κB and activator protein (AP-1). Interestingly, it was found that Ms-EE can directly suppress the enzyme activities of Syk, Src, and interleukin-1 receptor-associated kinase-1 (IRAK-1). Similarly, orally administered Ms-EE inhibited the phosphorylation of Src and Syk in peritoneal exudate-derived cells prepared from peritonitis. Finally, HPLC analysis clearly demonstrated that quercetin is a major active component with suppressing activity on the release of inflammatory mediators (NO and PGE2), and the enzyme activities of Src, Syk, and IRAK-1.

CONCLUSION

Ms-EE containing quercetin negatively modulates macrophage-mediated in vitro inflammatory responses and LPS-induced peritonitis by blocking the Src/Syk/NF-κB and IRAK-1/AP-1 pathways, which contributes to its major ethnopharmacological use as an anti-inflammatory herbal medicine.

p38/AP-1 pathway in lipopolysaccharide-induced inflammatory responses is negatively modulated by electrical stimulation

Electrical stimulation with a weak current has been demonstrated to modulate various cellular and physiological responses, including the differentiation of mesenchymal stem cells and acute or chronic physical pain. Thus, a variety of investigations regarding the physiological role of nano- or microlevel currents at the cellular level are actively proceeding in the field of alternative medicine. In this study, we focused on the anti-inflammatory activity of aluminum-copper patches (ACPs) under macrophage-mediated inflammatory conditions. ACPs generated nanolevel currents ranging from 30 to 55 nA in solution conditions. Interestingly, the nanocurrent-generating aluminum-copper patches (NGACPs) were able to suppress both lipopolysaccharide-(LPS-) and pam3CSK-induced inflammatory responses such as NO and PGE2 production in both RAW264.7 cells and peritoneal macrophages at the transcriptional level. Through immunoblotting and immunoprecipitation analyses, we found that p38/AP-1 could be the major inhibitory pathway in the NGACP-mediated anti-inflammatory response. Indeed, inhibition of p38 by SB203580 showed similar inhibitory activity of the production of TNF- α and PGE2 and the expression of TNF- α and COX-2 mRNA. These results suggest that ACP-induced nanocurrents alter signal transduction pathways that are involved in the inflammatory response and could therefore be utilized in the treatment of various inflammatory diseases such as arthritis and colitis.

C57BL/6 mice need MHC class II Aq to develop collagen-induced arthritis dependent on autoreactive T cells

INTRODUCTION

Collagen-induced arthritis (CIA) has traditionally been performed in MHC class II A(q)-expressing mice, whereas most genetically modified mice are on the C57BL/6 background (expressing the b haplotype of the major histocompatibility complex (MHC) class II region). However, C57BL/6 mice develop arthritis after immunisation with chicken-derived collagen type II (CII), but arthritis susceptibility has been variable, and the immune specificity has not been clarified.

OBJECTIVE

To establish a CIA model on the C57BL/6 background with a more predictable and defined immune response to CII.

RESULTS

Both chicken and rat CII were arthritogenic in C57BL/6 mice provided they were introduced with high doses of Mycobacterium tuberculosis adjuvant. However, contaminating pepsin was strongly immunogenic and was essential for arthritis development. H-2(b)-restricted T cell epitopes on chicken or rat CII could not be identified, but expression of A(q) on the C57BL/6 background induced T cell response to the CII260-270 epitope, and also prolonged the arthritis to be more chronic.

CONCLUSIONS

The putative (auto)antigen and its arthritogenic determinants in C57BL/6 mice remains undisclosed, questioning the value of the model for addressing T cell-driven pathological pathways in arthritis. To circumvent this impediment, we recommend MHC class II congenic C57BL/6N.Q mice, expressing A(q), with which T cell determinants have been thoroughly characterised.

In vitro and in vivo anti-inflammatory activities of Polygonum hydropiper methanol extract

ETHNOPHARMACOLOGICAL RELEVANCE

Polygonum hydropiper L. (Polygonaceae) has been traditionally used to treat various inflammatory diseases such as rheumatoid arthritis. However, no systematic studies on the anti-inflammatory actions of Polygonum hydropiper and its inhibitory mechanisms have been reported. This study is therefore aimed at exploring the anti-inflammatory effects of 99% methanol extracts (Ph-ME) of this plant.

MATERIALS AND METHODS

The effects of Ph-ME on the production of inflammatory mediators in RAW264.7 cells and peritoneal macrophages were investigated. Molecular mechanisms underlying the effects, especially inhibitory effects, were elucidated by analyzing the activation of transcription factors and their upstream signalling, and by evaluating the kinase activities of target enzymes. Additionally, a dextran sulphate sodium (DSS)-induced colitis model was employed to see whether this extract can be used as an orally available drug.

RESULTS

Ph-ME dose-dependently suppressed the release of nitric oxide (NO), tumour necrosis factor (TNF)-α, and prostaglandin (PG)E(2), in RAW264.7 cells and peritoneal macrophages stimulated by lipopolysaccharide (LPS). Ph-ME inhibited mRNA expression of pro-inflammatory genes such as inducible NO synthase (iNOS), cyclooxygenase (COX)-2, and TNF-α by suppressing the activation of nuclear factor (NF)-κB, activator protein (AP-1), and cAMP responsive element binding protein (CREB), and simultaneously inhibited its upstream inflammatory signalling cascades, including cascades involving Syk, Src, and IRAK1. Consistent with these findings, the extract strongly suppressed the kinase activities of Src and Syk. Based on HPLC analysis, quercetin, which inhibits NO and PGE(2) activities, was found as one of the active ingredients in Ph-ME.

CONCLUSION

Ph-ME exerts strong anti-inflammatory activity by suppressing Src/Syk/NF-κB and IRAK/AP-1/CREB pathways, which contribute to its major ethno-pharmacological role as an anti-gastritis remedy.

The ability of an ethanol extract of Cinnamomum cassia to inhibit Src and spleen tyrosine kinase activity contributes to its anti-inflammatory action

ETHNOPHARMACOLOGICAL RELEVANCE

Cinnamomum cassia Blume (Aceraceae) has been traditionally used to treat various inflammatory diseases such as gastritis. However, the anti-inflammatory mechanism of Cinnamomum cassia has not been fully elucidated. This study examined the anti-inflammatory mechanism of 95% ethanol extract (Cc-EE) of Cinnamomum cassia.

MATERIALS AND METHODS

The effect of Cc-EE on the production of inflammatory mediators in RAW264.7 cells and peritoneal macrophages was investigated. Molecular mechanisms underlying the effects, especially inhibitory effects, was elucidated by analyzing the activation of transcription factors and their upstream signaling, and by evaluating the kinase activity of target enzymes.

RESULTS

Cc-EE of Cinnamomum cassia diminished the production of nitric oxide (NO), tumor necrosis factor (TNF)-α, and prostaglandin (PG)E(2), in lipopolysaccharide (LPS)-activated RAW264.7 cells and peritoneal macrophages in a dose-dependent manner. Cc-EE also blocked mRNA expression of inducible NO synthase (iNOS), cyclooxygenase (COX)-2, and TNF-α by suppressing the activation of nuclear factor (NF)-κB, and simultaneously inhibited its upstream inflammatory signaling cascades, including spleen tyrosine kinase (Syk) and Src. Consistent with these findings, the extract directly blocked the kinase activities of Src and Syk.

CONCLUSION

Cc-EE exerts strong anti-inflammatory activity by suppressing Src/Syk-mediated NF-κB activation, which contributes to its major ethno-pharmacological role as an anti-gastritis remedy. Future work will be focused on determining whether the extract can be further developed as an anti-inflammatory drug.

Nanostructured, self-assembling peptide K5 blocks TNF-α and PGE₂ production by suppression of the AP-1/p38 pathway

Nanostructured, self-assembling peptides hold promise for a variety of regenerative medical applications such as 3D cell culture systems, accelerated wound healing, and nerve repair. The aim of this study was to determine whether the self-assembling peptide K5 can be applied as a carrier of anti-inflammatory drugs. First, we examined whether the K5 self-assembling peptide itself can modulate various cellular inflammatory responses. We found that peptide K5 significantly suppressed the release of tumor-necrosis-factor- (TNF-) α and prostaglandin E₂ (PGE₂) from RAW264.7 cells and peritoneal macrophages stimulated by lipopolysaccharide (LPS). Similarly, there was inhibition of cyclooxygenase- (COX-) 2 mRNA expression assessed by real-time PCR, indicating that the inhibition is at the transcriptional level. In agreement with this finding, peptide K5 suppressed the translocation of the transcription factors activator protein (AP-1) and c-Jun and inhibited upstream inflammatory effectors including mitogen activated protein kinase (MAPK), p38, and mitogen-activated protein kinase kinase 3/6 (MKK 3/6). Whether this peptide exerts its effects via a transmembrane or cytoplasmic receptor is not clear. However, our data strongly suggest that the nanostructured, self-assembling peptide K5 may possess significant anti-inflammatory activity via suppression of the p38/AP-1 pathway.

JNK1, but not JNK2, is required in two mechanistically distinct models of inflammatory arthritis

The roles of the c-Jun N-terminal kinases (JNKs) in inflammatory arthritis have been investigated; however, the roles of each isotype (ie, JNK1 and JNK2) in rheumatoid arthritis and conclusions about whether inhibition of one or both is necessary for amelioration of disease are unclear. By using JNK1- or JNK2-deficient mice in the collagen-induced arthritis and the KRN T-cell receptor transgenic mouse on C57BL/6 nonobese diabetic (K/BxN) serum transfer arthritis models, we demonstrate that JNK1 deficiency results in protection from arthritis, as judged by clinical score and histological evaluation in both models of inflammatory arthritis. In contrast, abrogation of JNK2 exacerbates disease. In collagen-induced arthritis, the distinct roles of the JNK isotypes can, at least in part, be explained by altered regulation of CD86 expression in JNK1- or JNK2-deficient macrophages in response to microbial products, thereby affecting T-cell-mediated immunity. The protection from K/BxN serum-induced arthritis in Jnk1(-/-) mice can also be explained by inept macrophage function because adoptive transfer of wild-type macrophages to Jnk1(-/-) mice restored disease susceptibility. Thus, our results provide a possible explanation for the modest therapeutic effects of broad JNK inhibitors and suggest that future therapies should selectively target the JNK1 isoform.

Cystatin C influences the autoimmune but not inflammatory response to cartilage type II collagen leading to chronic arthritis development

Introduction

Collagen-induced arthritis (CIA) is a mouse model for rheumatoid arthritis (RA) and is induced after immunization with type II collagen (CII). CIA, like RA, is an autoimmune disease leading to destruction of cartilage and joints, and both the priming and inflammatory phases have been suggested to be dependent on proteases. In particular, the cysteine proteases have been proposed to be detrimental to the arthritic process and even immunomodulatory. A natural inhibitor of cysteine proteases is cystatin C.

Methods

Cystatin C-deficient, sufficient and heterozygous mice were tested for onset, incidence and severity of CIA. The effect of cystatin C-deficiency was further dissected by testing the inflammatory effector phase of CIA; that is, collagen antibody-induced arthritis model and priming phase, that is, T cell response both in vivo and in vitro. In addition, in order to determine the importance of T cells and antigen-presenting cells (APCs), these cell populations were separated and in vitro T cell responses determined in a mixed co-culture system. Finally, flow cytometry was used in order to further characterize cell populations in cystatin C-deficient mice.

Results

Here, we show that mice lacking cystatin C, develop arthritis at a higher incidence and an earlier onset than wild-type controls. Interestingly, when the inflammatory phase of CIA was examined independently from immune priming then cystatin C-deficiency did not enhance the arthritis profile. However, in line with the enhanced CIA, there was an increased T cell and B cell response as delayed-type hypersensitivity reaction and anti-CII antibody titers were elevated in the cystatin C-deficient mice after immunization. In addition, the ex vivo naïve APCs from cystatin C-deficient mice had a greater capacity to stimulate T cells. Interestingly, dendritic cells had a more activated phenotype in naïve cystatin C-deficient mice.

Conclusions

The lack of cystatin C enhances CIA and primarily affects in vivo priming of the immune system. Although the mechanism of this is still unknown, we show evidence for a more activated APC compartment, which would elevate the autoimmune response towards CII, thus resulting in an enhanced development of chronic arthritis.

In vitro and in vivo anti-inflammatory effects of ethanol extract from Acer tegmentosum

AIM OF STUDY

Acer tegmentosum has been traditionally used for folk medicine to treat hepatic disorders such as hepatitis, hepatic cancer, and hepatic cirrhosis. In this study, we demonstrate the ethno-pharmacological activity of Acer tegmentosum in in vitro and in vivo inflammatory conditions.

RESULTS

The 70% ethanol extract (At-EE) of Acer tegmentosum dose-dependently diminished the production of nitric oxide (NO), tumour necrosis factor (TNF)-alpha, and prostaglandin (PG)E(2), in lipopolysaccharide (LPS)-activated RAW264.7 cells and peritoneal macrophages, by a transcriptional mechanism. At-EE also suppressed the activation of nuclear factor (NF)-kappaB, activator protein (AP)-1, and cAMP-responsive element binding (CREB), and simultaneously blocked their upstream inflammatory signalling cascades, including Akt, p38, and JNK. Furthermore, At-EE protected against LPS-induced cell death induced by reactive oxygen species (ROS) and reactive nitrogen species (RNS) and neutralized reactive species generation. In agreement with the in vitro results, orally administered At-EE strongly ameliorated ear oedema formation induced by arachidonic acid.

CONCLUSION

At-EE displays strong anti-inflammatory activities in vitro and in vivo, contributing to its major ethno-pharmacological role such as anti-hepatitis remedy and may be applicable to novel anti-inflammatory therapeutics.

Systemic administration of tolerogenic dendritic cells ameliorates murine inflammatory arthritis

The expression of various cell surface molecules and the production of certain cytokines are important mechanisms by which dendritic cells (DC) are able to bias immune responses. This paper describes the effects of the inflammatory cytokine tumor necrosis factor (TNF)-α on DC phenotype and function. TNF-α treatment resulted in upregulation of MHC class II and CD86 in the absence of increased cell surface CD40 and CD80 or the production of IL-12. Additionally TNF-α treated cells were able to bias T cell responses towards an anti-inflammatory profile. On a note of caution this tolerogenic phenotype of the DC was not stable upon subsequent TLR-4 ligation as a 4 hour pulse of the TNF-α treated DC with lipopolysaccharide (LPS) resulted in the restoration of IL-12 production and an enhancement of their T cell stimulatory capacity which resulted in an increased IFN-γ production. However, TNF-α treated DC, when administered in vivo, were shown to ameliorate disease in collagen induced arthritis, an experimental model of inflammatory joint disease. Mice receiving TNF-α treated DC but not LPS matured DC had a delayed onset, and significantly reduced severity, of arthritis. Disease suppression was associated with reduced levels of collagen specific IgG2a and decreased inflammatory cell infiltration into affected joints. In summary the treatment of DC with TNF-α generates an antigen presenting cell with a phenotype that can reduce the pro-inflammatory response and direct the immune system towards a disease modifying, anti-inflammatory state.

In vitro and in vivo anti-inflammatory effects of taheebo, a water extract from the inner bark of Tabebuia avellanedae

AIM OF STUDY

Tabebuia spp. (Bignoniaceae) are native to tropical rain forests throughout Central and South America and have long been used as a folk medicine to treat bacterial infection, blood coagulation, cancer and inflammatory diseases. In this study, we aimed to demonstrate the ethnopharmacological activity of Tabebuia avellanedae in various in vitro and in vivo inflammatory conditions.

MATERIALS AND METHODS

To do this, LPS-stimulated macrophages and arachidonic acid or croton oil-induced mouse ear edema models were employed.

RESULTS

The water extract (taheebo) of Tabebuia avellanedae significantly suppressed the production of prostaglandin (PG) E(2) and nitric oxide (NO), and blocked the mRNA expression of their catalyzing enzymes (cyclooxygenase [COX)-II] and inducible NO synthase [iNOS], respectively), in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. The blockade of inflammatory mediators by taheebo seemed to be the result of the interruption of extracellular signal-related kinase (ERK) activation, according to immunoblotting analysis and the NO assay, where LPS strongly induced the phosphorylation (a hallmark of activation) of ERK, and U0126, a selective ERK inhibitor, was found to strongly inhibit PGE(2) production. Similarly, oral administration of taheebo (100mg/kg) for 1 week completely diminished mouse ear edema induced by arachidonic acid, an activator of COX-II, but not croton oil, an activator of lipoxygenase.

CONCLUSIONS

These data suggest that the ethnopharmacological action of taheebo may be due to its negative modulation of macrophage-mediated inflammatory responses by suppressing PGE(2) production. Thus, this water extract may be developed as a new therapeutic remedy for various inflammatory diseases such as arthritis and atherosclerosis.

Cells of the synovium in rheumatoid arthritis. Dendritic cells

Dendritic cells are the major antigen-presenting and antigen-priming cells of the immune system. We review the antigen-presenting and proinflammatory roles played by dendritic cells in the initiation of rheumatoid arthritis (RA) and atherosclerosis, which complicates RA. Various signals that promote the activation of NF-κB and the secretion of TNF and IL-1 drive the maturation of dendritic cells to prime self-specific responses, and drive the perpetuation of synovial inflammation. These signals may include genetic factors, infection, cigarette smoking, immunostimulatory DNA and oxidized low-density lipoprotein, with major involvement of autoantibodies. We propose that the pathogenesis of RA and atherosclerosis is intimately linked, with the vascular disease of RA driven by similar and simultaneous triggers to NF-κB.

In vitro immunoregulatory effects of Korean mistletoe lectin on functional activation of monocytic and macrophage-like cells

Korean mistletoe lectin (KML) is one of the major active components in Viscum album var. (coloratum), displaying various biological effects such as anti-tumor and anti-metastatic activities. Even though it has been shown to boost host immune defense mechanisms, the immunomodulatory effects of KML on specific immune responses mediated by macrophages have not been fully elucidated. Therefore, in this study, we aimed to demonstrate KML's regulatory roles on macrophage-mediated immune responses. KML clearly blocked lipopolysaccharide (LPS)-induced events [expression of interleukin (IL)-10, nitric oxide (NO) production and phagocytic uptake], and suppressed the normal expression levels of IL-10 (at 2 ng/ml) and tumor necrosis factor (TNF)-alpha (at 10 ng/ml). In contrast, (1) the expression of cytokine (TNF-alpha) and (2) the generation of reactive oxygen species (ROS) induced by LPS were significantly up-regulated with KML co-treatment. In addition, KML itself increased the mRNA levels of IL-3 and IL-23; phagocytic uptake; the surface levels of co-stimulatory molecules (CD80 and CD86), pattern recognition receptors (PRRs) [such as dectin-1 and toll like receptor (TLR)-2] and adhesion molecules [beta1-integrins (CD29) and CD43]; and CD29-mediated cell adhesion events. Finally, according to co-treatment of D-galactose with KML under LPS-induced NO production conditions, KML inhibition seems to be mediated by binding to proteins with D-galactose. Therefore, these data suggest that KML may participate in regulating various macrophage-mediated innate and adaptive responses via binding to surface protein with D-galactose and that some of these may deserve in KML's therapeutic activities such as anti-tumor and anti-microbial effects.

Immunomodulatory effect of Hibiscus cannabinus extract on macrophage functions

Hibiscus cannabinus L. (Malvaceae) (known as Kenaf) has long been used as a folk medicine in India and Africa for the treatment of blood and throat disorders, bilious conditions, fever and puerperium. In this study, therefore, we aimed either to demonstrate its ethnopharmacological activity by examining its macrophage function-regulating effects or to expand its therapeutic efficacy into other macrophage-mediated diseases. The total crude extract (EtOH extract) of Hibiscus cannabinus fresh leaves, prepared with 80% ethanol, significantly suppressed TNF-alpha production and the mRNA expression of interleukin (IL)-3 and IL-12 in the RAW264.7 cells, stimulated by lipopolysaccharide (LPS, 2.5 microg/ml). The secretion of inflammatory mediators (i.e., nitric oxide [NO], reactive oxygen species [ROS] and prostaglandin E(2) [PGE(2)]) was diminished by the EtOH extract. The extract induced the expression of heme oxygenase-1 (HO-1) mRNA, a potent cytoprotective molecule. The Kenaf extract suppressed both the phagocytic uptake and the expression of costimulatory molecules (CD80 and CD86) of LPS-activated RAW264.7 cells. It is interesting that Kenaf also down-regulated both the functional activation of beta1-integrin (CD29) and the LPS-induced up-regulation of the surface CD29 level. Taken together, these data suggest that Kenaf may be able to modulate macrophage-mediated responses and that some of the activities may contribute to expand its therapeutic usage.

Extra-pulmonary aspects of acquired pulmonary alveolar proteinosis as predicted by granulocyte-macrophage colony-stimulating factor-deficient mice

Granulocyte-macrophage colony-stimulating factor (GM-CSF)-/- mice are an invaluable model for exploring the effects of systemic GM-CSF deficiency. Their lung phenotype exactly reproduces the abnormalities seen in human pulmonary alveolar proteinosis (PAP). However, GM-CSF-/- mice also have significant systemic functional abnormalities. These include immune defects which result in a reduced susceptibility to a range of experimentally induced autoimmune disorders. These immunological defects are also functionally manifest as an impaired ability to resolve a range of infections under certain conditions, usually implicating cellular effectors, including Listeria, Group B streptococcus, adenovirus, Pneumocystis carinii, and malaria. These observations are consistent with the known propensity for patients with PAP to develop a range of opportunistic infections. Conversely, the diminished immunological response to inflammatory stimuli may be beneficial in some settings by limiting inflammatory cell recruitment and pro-inflammatory mediator-release. GM-CSF-/- mice also have distinct fertility defects, manifest as reduced litter size and an increased rate of early fetal loss. These observations may be clinically relevant for women affected by PAP and further support the evaluation of the role of GM-CSF in human reproduction. These observations reinforce the importance of clinicians viewing PAP as a state of systemic functional GM-CSF deficiency, albeit with prominent pulmonary manifestations, rather than purely a 'lung disease'. These systemic manifestations of GM-CSF deficiency should also be considered when deciding on the choice between pulmonary or systemic delivery of GM-CSF as therapy for PAP, as only systemic drug delivery has the potential capacity to correct the systemic manifestations of GM-CSF deficiency in these patients.

The impact of glycosylation on HLA-DR1-restricted T cell recognition of type II collagen in a mouse model

OBJECTIVE

Type II collagen (CII) is a candidate autoantigen implicated in the pathogenesis of rheumatoid arthritis (RA). Posttranslational glycosylation of CII could alter intracellular antigen processing, leading to the development of autoimmune T cell responses. To address this possibility, we studied the intracellular processing of CII for presentation of the arthritogenic glycosylated epitope CII(259-273) to CD4 T cells in macrophages from HLA-DR1-transgenic mice.

METHODS

HLA-DR1-transgenic mice were generated on a class II major histocompatibility complex-deficient background, and T cell hybridomas specific for the glycosylated and nonglycosylated epitope CII(259-273) were developed. Subcellular fractionation of macrophages was used to localize CII degradation to particular compartments and to identify the catalytic subtype of proteinases involved.

RESULTS

We showed that the glycosylated CII(259-273) epitope required more extensive processing than did the nonglycosylated form of the same epitope. Dense fractions containing lysosomes were primarily engaged in the processing of CII for antigen presentation, since these compartments contained 1) enzyme activity that generated antigenic CII fragments bearing the arthritogenic glycosylated epitope, 2) the antigenic CII fragments themselves, 3) CII peptide-receptive HLA-DR1 molecules, and 4) peptide/HLA-DR1 complexes that could directly activate T cell hybridomas. Degradation of CII by dense fractions occurred optimally at pH 4.5 and was abrogated by inhibitors of serine and cysteine proteinases.

CONCLUSION

Processing of the arthritogenic glycosylated CII(259-273) epitope, which is implicated in the induction of autoimmune arthritis, is more stringently regulated than is processing of the nonglycosylated form of the same epitope. Mechanisms of intracellular processing of the glycosylated epitope may constitute novel therapeutic targets for the treatment of RA.

The major T cell epitope on type II collagen is glycosylated in normal cartilage but modified by arthritis in both rats and humans

Type II collagen (CII) is a target for autoreactive T cells in both rheumatoid arthritis and the murine model collagen-induced arthritis. The determinant core of CII has been identified as CII260-270, and the alteration of this T cell epitope by posttranslational modifications is known to be critical for development of arthritis in mice. Using CII-specific T cell hybridomas we have now shown that the immunodominant T cell epitope in the normal (healthy) human and rat joint cartilage is O-glycosylated at the critical T cell receptor recognition position 264 with a mono- or di-saccharide attached to a hydroxylysine. In contrast, in the arthritic human and rat joint cartilage there are both glycosylated and non-glycosylated CII forms. Glycosylated CII from normal cartilage could not be recognized by T cells reactive to peptides having only lysine or hydroxylysine at position 264, showing that antigen-presenting cells could not degrade the O-linked carbohydrate. Thus, the variable forms of the glycosylated epitope are determined by the structures present in cartilage, and these vary during the disease course. We conclude that the chondrocyte determines the structures presented to the immune system and that these structures are different in normal versus arthritic states.

Detection of CD4+Autoreactive T Cells in T1D Using HLA Class II Tetramers

The use of soluble class II MHC tetramers has enabled the identification of autoantigen-specific T cells in the peripheral blood of type 1 diabetes patients. Our approach takes advantage of the appearance of highly activated T cells expressing a CD25(+)/CD4(high+) phenotype induced by immobilized class II MHC monomer containing the GAD65 peptide. Almost all T cells that stain with the specific tetramer reside in this population and, since this activation profile is not present in normal subjects, it may provide a useful tool for analysis of the T cell response in autoimmune diabetes. The utilization of tetramer techniques in the detection of autoreactive T cells is a powerful tool to gain insight into mechanisms of the molecular basis of autoimmunity. The phenotyping of T cells should provide useful markers for progression of immune-mediated beta cell reactivity and can be utilized in clinical trials to evaluate the efficacy of the immunomodulatory therapies targeting intervention/prevention of autoimmune diseases.

Differential MHC class II-mediated presentation of rheumatoid arthritis autoantigens by human dendritic cells and macrophages

Rheumatoid arthritis is characterized by synovial joint infiltration of activated CD4(+) T cells and MHC class II(+) APC, and is linked to specific HLA-DR alleles. Candidate autoantigens in synovial fluid and cartilage include type II collagen (CII) and cartilage gp39 (HCgp39). Using preparations of native Ag and T cells derived from Ag-immunized DR4-transgenic mice, we determined that human ex vivo differentiated DR4(+) dendritic cells (DC) and macrophages (Mphi) can mediate MHC class II presentation of CII or HCgp39 epitopes. The form of the Ag (soluble, partially degraded, or particulate) delivered to the APC influenced its presentation by DC and Mphi. DC efficiently presented partially degraded, but not native CII alpha-chains, while Mphi presentation was most efficient after phagocytosis of bead-conjugated CII. Both DC and Mphi presented soluble HCgp39, and activated Mphi from some donors presented epitopes derived from endogenously synthesized HCgp39. When synovial fluid from rheumatoid arthritis patients was used as a source of Ag, DC presentation of HCgp39 and CII epitopes was efficient, indicating that synovial fluid contains soluble forms of CII and HCgp39 amenable to internalization, processing, and presentation. These data support the hypothesis that CII and HCgp39 are autoantigens and that their class II-mediated presentation by DC and Mphi to T cells in vivo has a critical role in the pathogenesis of human rheumatoid arthritis.

Detection of GAD65-specific T-cells by major histocompatibility complex class II tetramers in type 1 diabetic patients and at-risk subjects

Soluble HLA-DR401 or -DR404 tetramers containing a peptide corresponding to an immunodominant epitope from human GAD65 were used to analyze peripheral blood T-cells of newly diagnosed type 1 diabetic patients and at-risk subjects. Peripheral blood mononuclear cells were expanded on antigen-presenting cells presenting GAD65 peptide and subsequently activated with specific plate-bound class II-peptide monomers. T-cell activation defined in flow cytometry by CD4(high) and/or CD25 markers were observed in all type 1 diabetic patients and some at-risk subjects, but not in normal control subjects. The activated T-cells stained positive with tetramers containing the GAD65 epitope 555-567. Tetramer-positive cells were CD4(high) T-cells with high avidity for an immunodominant GAD65 T-cell epitope. Phenotyping of T-cells utilizing HLA class II tetramers provides a new tool to characterize the autoimmune response in type 1 diabetes.

Primed B cells present type-II collagen to T cells

Development of type-II collagen (CII)-induced arthritis (CIA) is dependent on a T-cell mediated activation of autoreactive B cells. However, it is still unclear if B cells can present CII to T cells. To investigate the role of B cells as antigen-presenting cells (APCs) for CII, we purified B cells from lymph nodes of immunized and nonimmunized mice. These B cells were used as APC for antigen-specific T-cell hybridomas. B cells from naïve mice did present native, triple-helical, CII (nCII) but also ovalbumin (OVA) and denatured CII (dCII) to antigen-specific T-cell hybridomas. In addition, B cells primed with nCII or OVA, but not dCII, activated the antigen-specific T-cell hybridomas two to three times better than naïve B cells. We conclude that antigen-primed B cells have the capacity to process and present CII to primed T cells, and antigen-primed antigen-specific B cells are more efficient as APC than naïve B cells. We further conclude that B cells have the potential to play an important role as APC in the development of CIA.

Antigen presentation of Type II collagen in rats

Collagen-induced arthritis (CIA) is a T-cell dependent disease of rats which follows immunization with bovine type II collagen (bCII). Susceptibility to CIA is linked to the genes encoding the major histocompatibility complex (MHC), suggesting that antigen presentation is important in disease pathogenesis. Antigen-presenting cells (APC) (macrophages, dendritic cells (DC) and B cells) were prepared from WA/KIR/KCL rats and presentation of antigen, in the form of native protein (bCII) or synthetic peptide (bCII:184-198), was assessed in T-cell proliferation assays. Whilst macrophages inhibited proliferative responses to bCII, splenic or thymic low density cells, enriched for DC, presented both bCII and bCII(184-198) peptide. However, bone marrow-derived DC, which stimulated T-cell responses to OVA, failed to present bCII, suggesting differences in processing of these two antigens. B-cell depletion from lymph node cells abrogated the proliferative response to bCII and reconstitution of a T-cell population with B cells restored the proliferative response, indicating that B cells are important for stimulating T-cell responses to bCII. B cells play a critical role in CIA by producing pathogenic anti-bCII antibodies, and we propose that B cells are also important APC which present bCII to CD4+ T cells.

H2-Mbeta 1 and H2-Mbeta 2 heterodimers equally promote clip removal in I-A(q) molecules from autoimmune-prone DBA/1 mice

Antigen-presenting cells degrade endocytosed antigens, e.g. collagen type II, into peptides that are bound and presented to arthritogenic CD4(+) helper T cells by major histocompatibility complex (MHC) class II molecules. Efficient loading of many MHC class II alleles with peptides requires the assistance of H2-M (HLA-DM in humans), a heterodimeric MHC class II-like molecule that facilitates CLIP removal from MHC class II molecules and aids to shape the peptide repertoire presented by MHC class II to CD4(+) T cells. In contrast to the HLA-DM region in humans, the beta-chain locus is duplicated in mice, with the H2-Mb1 beta-chain distal to H2-Mb2 and the H2-Ma alpha-chain gene. H2-M alleles appear to be associated with the development of autoimmune diseases. Recent data showed that Mbeta1 and Mbeta2 isoforms are differentially expressed in isolated macrophages and B cells, respectively. The tissue expression and functional role of these heterodimers in promoting CLIP removal and peptide selection have not been addressed. We utilized the human T2 cell line, which lacks part of chromosome 6 encompassing the MHC class II and DM genes, to construct transgenic cell lines expressing the MHC class II heterodimer I-A(q) alone or in the presence of H2-Malphabeta1 or H2-Malphabeta2 heterodimers. Both H2-M isoforms facilitate the exchange of CLIP for cognate peptides on I-A(q) molecules from arthritis-susceptible DBA/1 mice and induce a conformational change in I-A(q) molecules. Moreover, I-A(q) cell-surface expression is not absolutely dependent on H2-M molecules. These data suggest that I-A(q) exhibits a high affinity for CLIP since virtually all I-A(q) molecules on T2 cells were found to be associated with CLIP in the absence of both H2-M isoforms.

Validity of the two-signal model for activation of CD28-deficient T lymphocytes: quantitative characterization of an alternative costimulatory function of dendritic cells

The observation that primary T-dependent immune responses are generated in mice lacking CD28, the only receptor definitively shown to costimulate naive T cells, has led to ambiguity as to whether costimulation is absolutely required for initiation of T-cell responses. In this report, in vitro analysis of the relationship between cell density and proliferation demonstrates that activation of CD28-/- T cells to immobilized T-cell receptor (TCR)-alpha monoclonal antibodies (MoAb) depends on costimulatory signals provided by other cells in culture and occurs only at cell densities sufficient to permit these intercellular interactions. These signals are necessary even under TCR triggering conditions that obviate the CD28 requirement. Dendritic cells (DCs) provide the necessary costimulation in vitro and prime T cells in vivo in CD28-/- mice. Single-cell and limiting dilution analyses indicate that individual T cells from normal and CD28-/- mice produce equivalent interleukin (IL)-2 in response to DCs. However, half as many T cells produce IL-2 when only the CD28-independent pathway is used. Nonetheless, CD28-/- T cells produce sufficient IL-2 to support clonal expansion comparable to that of CD28+/+ T cells, which may account for the equally robust in vivo responses initiated by DCs in normal and CD28-deficient animals.

Distinct roles for the NF-kappaB1 (p50) and c-Rel transcription factors in inflammatory arthritis

Rheumatoid arthritis (RA) is a complex disease, with contributions from systemic autoimmunity and local inflammation. Persistent synovial joint inflammation and invasive synovial pannus tissue lead to joint destruction. RA is characterized by the production of inflammatory mediators, many of which are regulated by the Rel/NF-kappaB transcription factors. Although an attractive target for therapeutic intervention in inflammatory diseases, Rel/NF-kappaB is involved in normal physiology, thus global inhibition could be harmful. An alternate approach is to identify and target the Rel/NF-kappaB subunits critical for components of disease. To assess this, mice with null mutations in c-rel or nfkb1 were used to examine directly the roles of c-Rel and p50 in models of acute and chronic inflammatory arthritis. We found c-Rel-deficient mice were resistant to collagen-induced arthritis but had a normal response in an acute, destructive arthritis model (methylated BSA/IL-1 induced arthritis) suggesting c-Rel is required for systemic but not local joint disease. In contrast, p50-deficient mice were refractory to induction of both the chronic and acute arthritis models, showing this subunit is essential for local joint inflammation and destruction. Our data suggest Rel/NF-kappaB subunits play distinct roles in the pathogenesis of inflammatory arthritis and may provide a rationale for more specific therapeutic blockade of Rel/NF-kappaB in RA.

Macrophages in rheumatoid arthritis

The abundance and activation of macrophages in the inflamed synovial membrane/pannus significantly correlates with the severity of rheumatoid arthritis (RA). Although unlikely to be the 'initiators' of RA (if not as antigen-presenting cells in early disease), macrophages possess widespread pro-inflammatory, destructive, and remodeling capabilities that can critically contribute to acute and chronic disease. Also, activation of the monocytic lineage is not locally restricted, but extends to systemic parts of the mononuclear phagocyte system. Thus, selective counteraction of macrophage activation remains an efficacious approach to diminish local and systemic inflammation, as well as to prevent irreversible joint damage.

Engineering mouse T lymphocytes specific to type II collagen by transduction with a chimeric receptor consisting of a single chain Fv and TCR zeta

The chimeric cell surface receptor scC2Fv/CD8/zeta was constructed to engineer primary mouse T lymphocytes with antibody-type specificity to type II collagen (CII). Such cells could be used as gene carriers in the anti-inflammatory gene therapy of an autoimmune arthritis. This receptor includes the single chain Fv domain (scFv) of the anti-CII monoclonal antibody (mAb) C2, hinge region of CD8alpha and the transmembrane and cytoplasmic domains of TCRzeta. The scC2Fv/CD8/zeta gene was transduced into T cell hybridomas and primary mouse lymphocytes using retrovirus-mediated gene transfer. The chimeric receptor scC2Fv/CD8/zeta forms covalently bound homodimers, as demonstrated in T cell hybridomas and packaging fibroblasts. It does not associate with endogenous signalling subunits of the TCR complex. When scC2Fv/CD8/zeta-expressing clones of T cell hybridomas MD.45 and HCQ6 were stimulated with CII they produced IL-2. The level of their IL-2 response correlated with the expression level of the chimeric receptor on the cell surface. Splenocytes isolated from DBA/1 mice were stimulated with Con A in vitro to facilitate retrovirus-mediated transfer of the scC2Fv/CD8/zeta gene. As a result of transduction, approximately 4% of the Con A-activated splenocytes expressed the chimeric receptor scC2Fv/CD8/zeta on the cell surface. These cells proliferated in response to stimulation with CII.

T cells that are naturally tolerant to cartilage-derived type II collagen are involved in the development of collagen-induced arthritis

The immunodominant T-cell epitope that is involved in collagen-induced arthritis (CIA) is the glycosylated type II collagen (CII) peptide 256-270. In CII transgenic mice, which express the immunodominant CII 256-270 epitope in cartilage, the CII-specific T cells are characterized by a partially tolerant state with low proliferative activity in vitro, but with maintained effector functions, such as IFN-gamma secretion and ability to provide B cell help. These mice were still susceptible to CIA. The response was mainly directed to the glycosylated form of the CII 256-270 peptide, rather than to the nonglycosylated peptide. Tolerance induction was rapid; transferred T cells encountered CII within a few days. CII immunization several weeks after thymectomy of the mice did not change their susceptibility to arthritis or the induction of partial T-cell tolerance, excluding a role for recent thymic emigrants. Thus, partially tolerant CII autoreactive T cells are maintained and are crucial for the development of CIA.

Differential Presentation of Glutamic Acid Decarboxylase 65 (GAD65) T Cell Epitopes Among HLA-DRB1*0401-Positive Individuals

Glutamic acid decarboxylase 65 (GAD65) is one of the major autoantigens in type 1 diabetes. We investigated whether there is variation in the processing of GAD65 epitopes between individuals with similar HLA backgrounds and whether the processing characteristics of certain immunogenic epitopes are different in distinct APC subpopulations. Using DR401-restricted T cell hybridomas specific for two immunogenic GAD65 epitopes (115–127 and 274–286), we demonstrate an epitope-specific presentation pattern in human B-lymphoblastoid cell lines (B-LCL). When pulsed with the GAD protein, some DRB1*0401-positive B-LCL, which presented GAD65 274–286 epitope efficiently, were unable to present the GAD65 115–127 epitope. However, all B-LCL presented synthetic peptides corresponding to either GAD epitope. In addition, when pulsed with human serum albumin, all cell lines gave equal stimulation of a DR4-restricted human serum albumin-specific T hybridoma. GAD65-transfected cell lines displayed the same presentation phenotype, showing that lack of the presentation of the 115–127 epitope was not due to inefficient uptake of the protein. Blood mononuclear adherent cells, B cells, or dendritic cells derived from the same individual displayed the same presentation pattern as observed in B cell lines, suggesting that the defect most likely is genetically determined. Therefore, individual differences in Ag processing may result in the presentation of distinct set of peptides derived from an autoantigen such as GAD65. This may be an important mechanism for the deviation of the immune response either into a regulatory pathway or into an inflammatory autoimmune reactivity.

Differential expression of alternative H2-M isoforms in B cells, dendritic cells and macrophages by proinflammatory cytokines

Major histocompatibility (MHC) class II heterodimers bind peptides generated by degradation of endocytosed antigens and display them on the surface of antigen presenting cells (APCs) for recognition by CD4+ T cells. Efficient loading of MHC class II molecules with peptides is catalyzed by the MHC class II-like molecule H2-M. The coordinate regulation of MHC class II and H2-M expression is a prerequisite for efficient MHC class II/peptide assembly in APCs determining both the generation of the T cell repertoire in the thymus and cellular immune responses in the periphery. Here we show that expression of H2-M and MHC class II genes is coordinately and cell type-specific regulated in splenic B cells, splenic dendritic cells (DCs) and peritoneal macrophages (Mphi) in response to proinflammatory and immunoregulatory cytokines, including GM-CSF, IFN-gamma, TGF-beta2, IL-4, IL-10 and viral IL-10. In addition, ratio-RT-PCR expression analysis of the duplicated H2-Mbeta-chain loci demonstrates for the first time that Mbl and Mb2 genes are differentially expressed in individual APC types. Mb2 is preferentially expressed in IL-4, GM-CSF, IL-10, vIL-10 and IFN-gamma stimulated splenic B cells, whereas splenic DCs express both Mb genes at almost equal levels. In contrast, peritoneal Mphi express predominantly Mb2 but stimulation with IFN-gamma induces a switch towards Mb1 expression. These data suggest a common mechanism that regulates coordinate expression of H2-M and MHC class II genes in professional APCs. Differential expression of Mb1 and Mb2, and by consequence alternative H2-M isoforms (Malphabeta1 or Malphabeta2), may influence the nature of the peptide repertoire presented by different APC types.

Cytokine gene activation in synovial membrane, regional lymph nodes, and spleen during the course of rat adjuvant arthritis

Cytokine gene activation was assessed during rat adjuvant arthritis (AA) in synovial membrane (SM), popliteal lymph node (popl-LN), and spleen, using semiquantitative, competitive RT-PCR. Changes in the popl-LN were considerably higher than in spleen or SM. In the preclinical phase (day 6), cytokine mRNA elevations occurred exclusively in the popl-LN and included IFN-gamma, IL-1beta, IL-5, IL-6, and IL-10. In the acute phase (days 13-16) all three organs became involved: (i) in the SM, significant elevations were limited to IL-1beta and IL-6, which, notably, correlated positively with the degree of arthritis; (ii) in the popl-LN, IFN-gamma, IL-1beta, IL-6, and IL-10 (but not IL-5) were still elevated, while IL-2 rose significantly; (iii) in the spleen, TNF-alpha peaked simultaneously with the arthritis score (day 16) and dramatically dropped thereafter. Upon transition into the chronic phase (day 20) the following phenomena were observed: (i) IL-1beta and IL-6 were still significantly increased in the SM; (ii) IFN-gamma, IL-1beta, IL-2, IL-6, and IL-10 were still elevated in the popl-LN; and (iii) there was a progressive rise of IL-5 mRNA in the spleen, positively correlated with the arthritis score. In conclusion, cytokines with pro- and anti-inflammatory functions overlap throughout disease, but in different organ-related patterns. Local (SM) and regional (popl-LN) IL-1beta and IL-6, elevated throughout the entire course of AA, may directly contribute to disease severity. While in AA spleen TNF-alpha appears to be a systemic marker of acute disease, spleen IL-5 may be involved in disease resolution.

Human choriocarcinoma-derived JEG-3 cells transfected with murine MHC class II Aq expression vectors present antigen to Aq-restricted murine T-cell hybridoma

MHC class II molecules are not normally expressed on the cell surface of placental cells. This absence of class II molecules is assumed to be of importance for mammalian reproduction, since such expression is likely to increase the risk of harmful anti-placental immune responses. The present study was aimed to clarify whether post-transcriptional events prohibit proper cell surface expression of MHC class II molecules in cell lines of placental origin. The murine trophoblast cell line SM9-1 as well as the human choriocarcinoma-derived cell line JEG-3 were transiently co-transfected with MHC class II Aq a and b genes under the control of viral promoter systems. The transfected cells were stained for surface expression of MHC class II and assayed for antigen presentation in vitro. Only a small proportion of the transfected murine SM9-1 cells showed detectable class II cell surface expression, which made functional studies of this cell line difficult. The transfected JEG-3 cells, however, showed a high proportion of cells with distinct surface expression of murine class II Aq molecules and the antigen presentation assays revealed T cell activation upon addition of processed antigen, but not with unprocessed antigen. These results show that ectopic MHC class II gene transcription can result in cell surface expression of immunohistochemically detectable MHC class II on cells of placental origin. The fact that murine class II molecules could be expressed in a functional manner on human JEG-3 cells also strongly suggests that proper accessory gene activities are not essential for obtaining surface expression.

Classical MHC class I peptide presentation of a bacterial fusion protein by bone marrow-derived dendritic cells

Dendritic cells (DC) expanded in the presence of GM-CSF from the bone marrow of C57BL/6 mice process Gram-negative bacteria expressing the model antigen Crl-OVA for peptide presentation on MHC class I molecules. Here we show that presentation of OVA(257-264) processed by DC co-incubated with E. coli expressing Crl-OVA, which contains the Kb-binding OVA(257-264) epitope, occurs by a cytosolic MHC-I presentation pathway. First, we demonstrate the requirement for the transporter associated with antigen processing (TAP) by showing that DC from TAP1-/- mice co-incubated with E. coli expressing Crl-OVA did not result in Kb presentation of OVA(257-264). Second, the proteasome inhibitor MG132 abrogated presentation of OVA(257-264) on Kb when C57BL/6 DC phagocytosed and processed E. coli expressing Crl-OVA. Third, inhibiting protein synthesis using cycloheximide or blocking exocytosis of newly synthesized proteins from the endoplasmic reticulum using brefeldin A abrogated presentation of OVA(257-264) processed from bacteria expressing Crl-OVA by C57BL/6 DC. Finally, peptide regurgitation and loading of OVA(257-264) on neighboring bystander Kb-expressing antigen-presenting cells after BALB/c (H-2d) DC phagocytosed E. coli expressing Crl-OVA could not be detected. Together, these data support a cytosolic MHC-I presentation pathway for OVA(257-264) processed from E. coli expressing Crl-OVA by bone marrow-derived DC.

Protection from Collagen-Induced Arthritis in Granulocyte-Macrophage Colony-Stimulating Factor-Deficient Mice

The involvement of granulocyte-macrophage CSF (GM-CSF) in collagen-induced arthritis (CIA) was examined using GM-CSF-deficient mice. Although CIA is generally considered to be restricted to mice of the H-2q or H-2r haplotypes, we examined the role of GM-CSF in the CIA model using GM-CSF-deficient (−/−) and wild-type (+/+) mice on a C57BL/6 (H-2b) background. Mice were immunized by intradermal injection at the base of the tail with chick type II collagen followed by a repeat injection 21 days later. We found, based on both clinical and histologic assessments, that wild-type mice on this background developed severe CIA, while the GM-CSF-deficient mice had virtually no disease. Mice that were heterozygous for the GM-CSF gene (+/−) collectively displayed an intermediate response between those of the GM-CSF+/+ and GM-CSF−/− groups, suggesting a gene dosage effect. GM-CSF+/+ and GM-CSF+/− mice exhibited CIA responses ranging from mild (single digits) to severe swelling of all four paws, while in the few GM-CSF−/− mice that developed CIA the disease was confined to single digits. Despite the putative role of GM-CSF in dendritic cell development, GM-CSF-deficient mice exhibited both humoral and cellular (delayed-type hypersensitivity) responses to type II collagen; however, the cellular response was significantly reduced in the GM-CSF-deficient mice compared with the wild-type controls. These findings suggest that GM-CSF is required for CIA development in mice and support the idea that GM-CSF is a key cytokine in inflammatory joint disease.

Receptor for alpha1-microglobulin on T lymphocytes: inhibition of antigen-induced interleukin-2 production

The human plasma protein alpha1-microglobulin (alpha1m) was found to inhibit the antigen-induced interleukin-2 (IL-2) production of two different mouse T-helper cell hybridomas. Alpha1m isolated from human plasma and recombinant alpha1m isolated from baculovirus-infected insect cell cultures had similar inhibitory effects. Flow cytometric analysis showed a binding of plasma and recombinant alpha1m to the T-cell hybridomas as well as to a human T-cell line. Radiolabelled plasma and recombinant alpha1m bound to the T-cell hybridomas in a saturable manner and the binding could be eliminated by trypsination of the cells. The affinity constants for the cell binding were calculated to be 0.4-1 x 10(5) M(-1) using Scatchard plotting, and the number of binding sites per cell was estimated to be 5 x 10(5)-1 x 10(6). The cell-surface proteins of one of the T-cell hybridomas were radiolabelled, the cells lysed and alpha1m-binding proteins isolated by affinity chromatography. SDS-PAGE and autoradiography analysis of the eluate revealed major bands with Mr-values around 70, 35 and 15 kDa. The results thus suggest that alpha1m binds to a specific receptor on T cells and that the binding leads to inhibition of antigen-stimulated IL-2 production by T-helper cells.

Granulocyte-macrophage colony stimulating factor exacerbates collagen induced arthritis in mice

OBJECTIVE

To examine the effect of granulocyte-macrophage colony stimulating factor (GM-CSF) on disease progression in the collagen induced arthritis (CIA) model in mice.

METHODS

DBA/1 mice were primed for a suboptimal CIA response by intradermal injection of chick type II collagen without a secondary immunisation. Three weeks after immunisation the mice were given four to five consecutive daily intraperitoneal injections of recombinant murine GM-CSF (15 micrograms; 5 x 10(5) U), or vehicle, and arthritis development was monitored by clinical scoring of paws and calliper measurements of footpad swelling. At approximately six to eight weeks after immunisation mice were killed, their limbs removed and processed for histological analyses of joint pathology.

RESULTS

Control animals receiving a single immunisation with collagen exhibited a varied CIA response both in terms of incidence and severity. Mice treated with GM-CSF at 20 to 25 days after immunisation with collagen had a consistently greater incidence and more rapid onset of disease than the vehicle treated control mice, based on clinical assessment. GM-CSF treated mice showed higher average clinical scores and greater paw swelling than controls. Histological analyses of joints reflected the clinical scores with GM-CSF treated mice displaying more pronounced pathology (synovitis, pannus formation, cartilage and bone damage) than control mice.

CONCLUSION

GM-CSF is a potent accelerator of the pathological events leading to chronic inflammatory polyarthritis in murine CIA supporting the notion that GM-CSF may play a part in inflammatory polyarthritis, such as rheumatoid arthritis.