The Protective Antibodies Induced by a Novel Epitope of Human TNF-α Could Suppress the Development of Collagen-Induced Arthritis

Tumor necrosis factor alpha (TNF-α) is a major inflammatory mediator that exhibits actions leading to tissue destruction and hampering recovery from damage. At present, two antibodies against human TNF-α (hTNF-α) are available, which are widely used for the clinic treatment of certain inflammatory diseases. This work was undertaken to identify a novel functional epitope of hTNF-α. We performed screening peptide library against anti-hTNF-α antibodies, ELISA and competitive ELISA to obtain the epitope of hTNF-α. The key residues of the epitope were identified by means of combinatorial alanine scanning and site-specific mutagenesis. The N terminus (80–91 aa) of hTNF-α proved to be a novel epitope (YG1). The two amino acids of YG1, proline and valine, were identified as the key residues, which were important for hTNF-α biological function. Furthermore, the function of the epitope was addressed on an animal model of collagen-induced arthritis (CIA). CIA could be suppressed in an animal model by prevaccination with the derivative peptides of YG1. The antibodies of YG1 could also inhibit the cytotoxicity of hTNF-α. These results demonstrate that YG1 is a novel epitope associated with the biological function of hTNF-α and the antibodies against YG1 can inhibit the development of CIA in animal model, so it would be a potential target of new therapeutic antibodies.     

Down-regulation of murine collagen-induced arthritis by a T cell hybridoma

T cell hybridoma cell lines were generated by somatic cell fusion of BW 5147 myeloma cells and splenic cells from mice suppressed for collagen-induced arthritis (CIA). Two cell lines were characterized for their cell surface phenotype, antigen recognition and capacity to down-regulate the erythema and edema associated with CIA. Cell line T101N was determined to portray the cell surface phenotype Ly1+2- L3T4- Thy1+ by a direct binding assay. Cell line T104B1 was determined to express only the Thy1+ alloantigen. Panning studies, measurement of IL-2 production in vitro and the suppression of antibodies to type I and type II collagen in vivo indicate that the hybridoma cells are not isotype specific in their recognition of the polymorphic interstitial collagens. Down-regulation of the erythema and edema of CIA occurred on injection of 1 X 10(5) T101N cells but not T104B1 cells. Histology of the tarsus region of the hind paw of CIA mice 33 days after the administration of T101N cells showed contrasting histopathology compared to that of CIA mice. The joints of CIA mice given T101N cells showed aligned articular surfaces resembling normal joint structure and only residual pannus. The data indicate that collagen-specific cloned T cell lines can modulate the gross pathology and joint architecture of joints exhibiting CIA.     

Type II collagen-induced arthritis in mice. III. Suppression of arthritis by using monoclonal and polyclonal anti-Ia antisera

Pretreatment of mice genetically susceptible to type II collagen-induced arthritis (CIA) with monoclonal or polyclonal antisera specific for I region gene products (Ia antigens) suppressed or delayed the onset of CIA, whereas pretreatment with anti-Ia to an irrelevant haplotype was without effect. The humoral response to type II collagen was transiently depressed 14 days after immunization but antibody levels did not differ significantly after 28 days. The peak delayed-type hypersensitivity to type II collagen was unaffected by anti-Ia treatment. Monoclonal antibody of one anti-Ia specificity enhanced both the antibody response and the arthritis incidence in one mouse strain.     

Type II collagen antibody response is enriched in the synovial fluid of rheumatoid joints and directed to the same major epitopes as in collagen induced arthritis in primates and mice

Introduction

Antibodies towards type II collagen (CII) are detected in patients with rheumatoid arthritis (RA) and in non-human primates and rodents with collagen induced arthritis (CIA). We have previously shown that antibodies specific for several CII-epitopes are pathogenic using monoclonal antibodies from arthritic mice, although the role of different anti-CII epitopes has not been investigated in detail in other species. We therefore performed an inter-species comparative study of the autoantibody response to CII in patients with RA versus monkeys and mice with CIA.

Methods

Analysis of the full epitope repertoire along the disease course of CIA was performed using a library of CII triple-helical peptides. The antibody responses to the major CII epitopes were analyzed in sera and synovial fluid from RA patients, and in sera from rhesus monkeys (Macaca mulatta), common marmosets (Callithrix jacchus) and mice.

Results

Many CII epitopes including the major C1, U1, and J1 were associated with established CIA and arginine residues played an important role in the anti-CII antibody interactions. The major epitopes were also recognized in RA patients, both in sera and even more pronounced in synovial fluid: 77% of the patients had antibodies to the U1 epitope. The anti-CII immune response was not restricted to the anti-citrulline protein antibodies (ACPA) positive RA group.

Conclusion

CII conformational dependent antibody responses are common in RA and are likely to originate from rheumatoid joints but did not show a correlation with ACPA response. Importantly, the fine specificity of the anti-CII response is similar with CIA in monkeys and rodents where the recognized epitopes are conserved and have a major pathogenic role. Thus, anti-CII antibodies may both contribute to, as well as be the consequence of, local joint inflammation.     

Chronic development of collagen-induced arthritis is associated with arthritogenic antibodies against specific epitopes on type II collagen

Antibodies against type II collagen (CII) are important in the development of collagen-induced arthritis (CIA) and possibly also in rheumatoid arthritis. We have determined the fine specificity and arthritogenicity of the antibody response to CII in chronic relapsing variants of CIA. Immunization with rat CII in B10.Q or B10.Q(BALB/c×B10.Q)F₂ mice induces a chronic relapsing CIA. The antibody response to CII was determined by using triple-helical peptides of the major B cell epitopes. Each individual mouse had a unique epitope-specific response and this epitope predominance shifted distinctly during the course of the disease. In the B10.Q mice the antibodies specific for C1 and U1, and in the B10.Q(BALB/c×B10.Q)F₂ mice the antibodies specific for C1, U1 and J1, correlated with the development of chronic arthritis. Injection of monoclonal antibodies against these epitopes induced relapses in chronic arthritic mice. The development of chronic relapsing arthritis, initially induced by CII immunization, is associated with an arthritogenic antibody response to certain CII epitopes.     

Hepatocyte growth factor significantly suppresses collagen-induced arthritis in mice

Hepatocyte growth factor (HGF) plays an important role in angiogenesis, cell proliferation, antifibrosis, and antiapoptosis. Moreover, recent studies have highlighted the immunosuppressive effect of HGF in animal models of allogenic heart transplantation and autoimmune myocarditis and in studies in vitro as well. We also reported that HGF significantly suppresses dendritic cell function, thus down-regulating Ag-induced Th1-type and Th2-type immune responses in allergic airway inflammation. However, the immunosuppressive effect of HGF in many other situations has not been fully clarified. In the present study, using a mouse model of collagen-induced arthritis (CIA) and experiments in vitro, we examined the effect of HGF on autoimmune arthritis and then elucidated the mechanisms of action of HGF. To achieve sufficient delivery of HGF, we used biodegradable gelatin hydrogels as a carrier. HGF suppressed Ag-induced T cell priming by regulating the functions of dendritic cells in the Ag-sensitization phase with down-regulation of IL-10. In contrast, under continuous Ag stimulation HGF induced IL-10-producing immunocytes both in vivo and in vitro. Moreover, HGF potently inhibited the development of CIA with enhancing the Th2-type immune response. We also confirmed that HGF significantly suppressed the production of IL-17 by immunocytes. These results indicate that HGF suppresses the development of CIA through different ways at different phases. They also suggest that HGF could be an attractive tool for treating patients with rheumatoid arthritis.     

Prostaglandin and thromboxane in liposomes: suppression of the primary immune response to liposomal antigens

Liposomes containing lipid A as adjuvant and also containing prostaglandin E2 or thromboxane B2 were examined for the ability to influence induction of humoral immunity against liposomal protein or lipid antigens in rabbits. The protein antigen consisted of cholera toxin that was bound to ganglioside GM1 on the surface of the liposomes. High titers of anti-cholera toxin antibodies were produced and IgM and IgG responses were detected. When the immunizing liposomes contained either prostaglandin E2 or thromboxane B2 as part of the lipid bilayer, the primary immune response, involving both IgM and IgG antibodies, was greatly reduced. The secondary immune response observed after a boosting immunization was not suppressed by liposomal eicosanoids. A similar inhibitory effect on the primary response was observed when liposomal lipid antigens were examined instead of cholera toxin. An inhibitory effect of liposomal prostaglandin E2 on the phagocytic uptake of opsonized liposomes by cultured macrophages was also observed, suggesting that liposomal eicosanoids can have direct local effects on macrophages that might influence the immune response to liposomal antigens.     

Enforced Expression of Roquin Protein in T Cells Exacerbates the Incidence and Severity of Experimental Arthritis

To investigate the role of Roquin, a RING-type ubiquitin ligase family member, we used transgenic mice with enforced Roquin expression in T cells, with collagen-induced arthritis (CIA). Wild-type (WT) and Roquin transgenic (Tg) mice were immunized with bovine type II collagen (CII). Arthritis severity was evaluated by clinical score; histopathologic CIA severity; proinflammatory and anti-inflammatory cytokine levels; anti-CII antibody levels; and populations of Th1, Th2, germinal center B cells, and follicular helper T cells in CIA. T cell proliferation in vitro and cytokine levels were determined to assess the response to CII. Roquin Tg mice developed more severe CIA and joint destruction compared with WT mice. Production of TNF-α, IFN-γ, IL-6, and pathogenic anti-collagen CII-specific IgG and IgG2a antibodies was increased in Roquin Tg mice. In addition, in vitro T cell assays showed increased proliferation and proinflammatory cytokine production in response to CII as a result of enforced Roquin expression in T cells. Furthermore, the Th1/Th2 balance was altered by an increased Th1 and decreased Th2 population. These findings suggest that overexpression of Roquin exacerbates the development of CIA and that enforced expression of Roquin in T cells may promote autoimmune diseases such as CIA.     

Prophylactic Injection of Recombinant Alpha-Enolase Reduces Arthritis Severity in the Collagen-Induced Arthritis Mice Model

Objective

To evaluate the ability of the glycolytic enzyme alpha-enolase (ENO1) or its immunodominant peptide (pEP1) to reduce the severity of CIA in DBA/1 mice when injected in a prophylactic way.

Methods

Mice were treated with mouse ENO1 or pEP1 one day prior to collagen II immunization. Clinical assessment was evaluated using 4 parameters (global and articular scores, ankle thickness and weight). Titers of serum anti-ENO1, anti-cyclic citrullinated peptides (anti-CCP) and anti-CII (total IgG and IgG1/IgG2a isotypes) antibodies were measured by ELISA at different time-points. Disease activity was assessed by histological analysis of both anterior and hind paws at the end of experimentation.

Results

Prophylactic injection of 100 μg of ENO1 reduced severity of CIA. Serum levels of anti-CII antibodies were reduced in ENO1-treated mice. Concordantly, ENO1-treated mice joints presented less severe histological signs of arthritis. ENO1 did not induce a shift toward a Th2 response since IgG1/IgG2a ratio of anti-CII antibodies remained unchanged and IL-4 serum levels were similar to those measured in the control group.

Conclusions

Pre-immunization with ENO1 or its immunodominant peptide pEP1 reduces CIA severity at the clinical, immunological and histological levels. Effects of pEP1 were less pronounced. This immunomodulatory effect is associated with a reduction in anti-CII antibodies production but is not due to a Th1/Th2 shift.     

Role of Mls-1 locus and clonal deletion of T cells in susceptibility to collagen-induced arthritis in mice

The role of T cell-mediated and humoral immunity to type II collagen has been well documented in collagen-induced arthritis (CIA). Previous work from our laboratory has indicated that genomic deletions of TCR V beta genes may play a role in CIA resistance in mice. This indicated a selectivity of TCR usage by autoreactive T cells in CIA in mice. Certain strains of mice, although having a normal genomic V beta TCR repertoire, can show clonal deletion of peripheral T cells that bear specific V beta gene products in their TCR. These clonally deleted T cells are reactive with self-Ag such as minor lymphocyte stimulation (Mls) Ag. An Mls-congenic strain, BALB.D2.Mlsa, which differs only at the Mls-1 a locus from BALB/c (Mls-1b), was used to examine the effect of clonal deletion of Mls-1a-reactive T cells in CIA. These two strains were crossed to three CIA-susceptible strains, B10.RIII (H-2r, Mls-1b), DBA/1 (H-2q, Mls-1a), and B10.Q (H-2q, Mls-1b), and the crosses were injected with type II collagen. A significantly decreased incidence of arthritis was observed in the (BALB.D2.Mlsa x B10.Q)F1 hybrids, compared with (BALB/c x B10.Q)F1 hybrids, upon immunization with chick type II collagen. The BALB.D2.Mlsa cross mice also had significantly lower levels of antimouse collagen antibodies. Flow cytometric analysis confirmed the clonal deletion of Mls-1a-reactive V beta 8.1, V beta 6, V beta 7, and V beta 9 subsets in the (BALB.D2.Mlsa x B10.Q)F1 hybrids. The study of H-2q/d mice in (BALB.D2.Mlsa x B10.Q) x B10.Q back-crosses demonstrated a significant correlation between CIA resistance and Mls-1a locus. On the other hand, B10.RIII crosses showed only a modest decrease in CIA incidence in the presence of Mls-1a. As expected, all the DBA/1 crosses had an equal incidence of CIA, which was somewhat less than that seen in DBA/1 mice themselves. These studies point out that the Mls-1a locus could play a role in decreasing CIA incidence by clonal deletion of T cells bearing specific V beta TCR, which may be involved in the pathogenesis of CIA. The influence of the clonal deletion of T cells on CIA, and hence the usage of specific V beta TCR by autoreactive anti-type II collagen T cells, however, depends not only on the source of the type II collagen and the MHC class II molecules involved but also on other background genes in mice.     

IL-23 Dependent and Independent Stages of Experimental Arthritis: No Clinical Effect of Therapeutic IL-23p19 Inhibition in Collagen-induced Arthritis

IL-23p19 deficient mice have revealed a critical role of IL-23 in the development of experimental autoimmune diseases, such as collagen-induced arthritis (CIA). Neutralizing IL-23 after onset of CIA in rats has been shown to reduce paw volume, but the effect on synovial inflammation and the immunological autoimmune response is not clear. In this study, we examined the role of IL-23 at different stages of CIA and during T cell memory mediated flare-up arthritis with focus on changes in B cell activity and Th1/Th17 modulation. Anti-IL-23p19 antibody (anti-IL23p19) treatment, starting 15 days after the type II collagen (CII)-immunization but before clinical signs of disease onset, significantly suppressed the severity of CIA. This was accompanied with significantly lower CII-specific IgG1 levels and lower IgG2a levels in the anti-IL-23p19 treated mice compared to the control group. Importantly, neutralizing IL-23 after the first signs of CIA did not ameliorate the disease. This was in contrast to arthritic mice that underwent an arthritis flare-up since a significantly lower disease score was observed in the IL-23p19 treated mice compared to the control group, accompanied by lower synovial IL-17A and IL-22 expression in the knee joints of these mice. These data show IL-23-dependent and IL-23-independent stages during autoimmune CIA. Furthermore, the memory T cell mediated flare-up arthritis is IL-23-mediated. These data suggest that specific neutralization of IL-23p19 after onset of autoimmune arthritis may not be beneficial as a therapeutic therapy for patients with rheumatoid arthritis (RA). However, T cell mediated arthritis relapses in patients with RA might be controlled by anti-IL-23p19 treatment.     

Immune response to immunization via the anterior chamber of the eye. I. F. lymphocyte-induced immune deviation.

The immunizing abilities of alloantigens placed within the anterior chamber of the eye have been studied in inbred rats. Although intracameral inoculation of F1 hybrid lymphocytes into parental strain recipients elicited both cell- and antibody-mediated immunity, a delimited interval was identified postinoculation during which the systemic cell-mediated immune response was suppressed as indicated by prolonged acceptance of orthotopic skin allografts. The prompt appearance of hemagglutinating antibodies in the serum of immunized rats followed a time course which coincided with the suppression of cell-mediated immunity and suggested that the two events are casually related. Since exposure to allogeneic antigens on lymphoid cells via the anterior chamber elicits a transient suppression in cell-mediated immunity, where humoral immunity is preserved, the phenomenon resembles immune deviation.     

A recombinant vaccine effectively induces c5a-specific neutralizing antibodies and prevents arthritis

Objectives

To develop and validate a recombinant vaccine to attenuate inflammation in arthritis by sustained neutralization of the anaphylatoxin C5a.

Methods

We constructed and expressed fusion protein of C5a and maltose binding protein. Efficacy of specific C5a neutralization was tested using the fusion protein as vaccine in three different arthritis mouse models: collagen induced arthritis (CIA), chronic relapsing CIA and collagen antibody induced arthritis (CAIA). Levels of anti-C5a antibodies and anti-collagen type II were measured by ELISA. C5a neutralization assay was done using a rat basophilic leukemia cell-line transfected with the human C5aR. Complement activity was determined using a hemolytic assay and joint morphology was assessed by histology.

Results

Vaccination of mice with MBP-C5a led to significant reduction of arthritis incidence and severity but not anti-collagen antibody synthesis. Histology of the MBP-C5a and control (MBP or PBS) vaccinated mice paws confirmed the vaccination effect. Sera from the vaccinated mice developed C5a-specific neutralizing antibodies, however C5 activation and formation of the membrane attack complex by C5b were not significantly altered.

Conclusions

Exploitation of host immune response to generate sustained C5a neutralizing antibodies without significantly compromising C5/C5b activity is a useful strategy for developing an effective vaccine for antibody mediated and C5a dependent inflammatory diseases. Further developing of such a therapeutic vaccine would be more optimal and cost effective to attenuate inflammation without affecting host immunity.     

Regulatory effect of vasoactive intestinal peptide on the balance of Treg and Th17 in collagen-induced arthritis

Vasoactive intestinal peptide (VIP) is a well-known anti-inflammatory neuropeptide. The capacity of VIP can be exhibited through inhibiting inflammatory responses, shifting the Th1/Th2 balance in favor of anti-inflammatory Th2 immunity and inducing regulatory T cells (Tregs) with suppressive activity. In addition to pro-inflammatory Th1 response, Th17 are also believed to play important roles in the pathogenesis of rheumatoid arthritis (RA). In this study, we used collagen-induced arthritis (CIA) model in Wistar rats to investigate the role of VIP in the balance of CD4⁺ CD25⁺ Tregs and Th17 on RA. Data presented here showed that administration of VIP decreased incidence and severity of CIA. Disease suppression was associated with the upregulation of CD4⁺ CD25⁺ Tregs, downregulation of Th17- and Th1-type response and influence on the RANK/RANKL/OPG system. The results provide novel evidence that the therapeutic effects of VIP on CIA rats were associated with the balance of CD4⁺ CD25⁺ Tregs and Th17.     

Regulation of the immune response by antibody. II. The effects of different classes of passive guinea pig antibody on humoral and cell-mediated immunity in rats

The ability of different classes of passively administered guinea pig antibody (γ1, γ2, and IgM) to regulate humoral and cell-mediated immunity to flagellin, polymerized flagellin (POL), and sheep red blood cells (SRBC) was investigated in rats. It was found that at high concentrations, all classes of antibody suppressed the primary antibody responses and usually enhanced the delayed-type hypersensitivity induced by the three antigens. With flagellin and SRBC, the different classes of passive antibody varied in their suppressing and enhancing properties, being in the order: γ2 > γ1 = IgM. At low concentrations, γ1 and IgM enhanced the primary antibody response and suppressed the delayed hypersensitivity induced by flagellin. Such an effect was not observed with either POL or SRBC. Priming for a secondary antibody response was less readily suppressed by all classes of passive antibody. The removal of macrophage cytophilic antibody from γ2 converted this antibody to a preparation (γ2 absorbed) which had effects on humoral and cell-mediated immunity approaching that of γ1 antibody.     

Anti-tumor necrosis factor antibodies suppress cell-mediated immunity in vivo.

Rabbit anti-murine TNF-alpha antibodies were administered in vivo to mice to evaluate the role of TNF-alpha in T cell-mediated immunity. Anti-TNF suppressed the in vivo development of contact sensitivity to the hapten TNP in a dose-dependent fashion. Similarly anti-TNF suppressed the in vivo priming for TNP-specific CTL. Control antibodies did not suppress cell-mediated immunity, whereas purified murine rTNF-alpha neutralized the antibody activity. Antibody therapy was effective during the afferent or priming limb of immunity, but could not inhibit the response if administered during the efferent limb. FACS for CD2, CD3, CD4, and CD8 T, B, and NK cell surface markers demonstrated no major change in the distribution of splenic lymphoid cell populations in animals pretreated with anti-TNF antibody. These results suggest that anti-TNF antibody may be interfering with soluble cytokines rather than with cell surface TNF causing depletion of cell populations. In vitro analyses also showed that anti-TNF has minimal inhibitory effects on secondary (secondary CTL) or strong primary (primary CTL, alpha CD3, MLR) responses, even though these in vitro cultures produce TNF mRNA as shown by polymerase chain reaction amplification. Although anti-TNF antibody did not affect the above responses, primary interactions are strongly inhibited in vivo. These findings suggest that TNF is important during afferent, priming events in immunity and that inhibition of TNF receptor-ligand interactions may alter immunity early in a response. Conversely such inhibition is ineffective later in a response, perhaps due to the ability of multiple other receptor-ligand pathways to bypass TNF.     

Collagen-Induced Arthritis Suppressed with Monoclonal Anti-Idiotypic Antibody

In foregoing work, we identified at least 5 distinct epitopes on human type II collagen (CII), using 8 murine monoclonal antibodies (mAb) against human CII, and suggested that a species-nonspecific epitope on CII recognized by anti-CII mAb termed 1-5 is an arthritogenic epitope. We also found that antibody response against a selected epitope of human CII could be induced by immunization with rabbit anti-idiotypic (Id) antibody against anti-CII mAb. The author developed and characterized monoclonal anti-Id antibodies against 1-5 mAb recognizing a putative arthritogenic epitope. The author also investigated whether the anti-Id mAb could regulate antibody response directed against a selected epitope recognized by 1-5 mAb, and the induction of collagen-induced arthritis in DBA/1J mice. DBA/1J mice intravenously preinjected with anti-Id mAb to 1-5, did not produce anti-CII antibody expressing 1-5 Id upon immunization with human CII. Furthermore, as the development of collagen-induced arthritis (CIA) in DBA/1J mice pretreated with anti-Id mAb to 1-5 was significantly suppressed, anti-Id mAb will be a useful tool for studying the regulation of antibody response to a selected epitope. This study lends support to our hypothesis that the 1-5 epitope is an arthritogenic epitope.     

禁食时间对雌性长爪沙鼠免疫功能的影响

动物的免疫系统是防御细菌、病毒等病原体侵害的重要途径,对其生存很重要,而食物短缺是影响动物免疫的重要因素。前期研究发现,禁食3天可抑制雌性长爪沙鼠T细胞介导的免疫功能,而禁食时长可能在影响动物免疫中起重要作用。为此,本实验主要测定不同的禁食时间如何影响雌性长爪沙鼠的免疫功能,该问题的解决有助于理解它们在野外面临食物短缺时的生存状况。将55只成年雌鼠随机分为8组,分别禁食1 d、2 d 、3 d和自由取食,每种处理又分别注射磷酸缓冲液和植物血凝素（PHA）。结果发现,随禁食时间的延长,PHA反应（指示T细胞介导的免疫功能）逐渐受到抑制,胸腺和脾脏逐渐萎缩,表明禁食时间对长爪沙鼠的免疫功能影响显著。同样,随饥饿时间增加,长爪沙鼠的体脂、血糖和血清瘦素水平逐渐下降,并且与PHA反应呈正相关,但白细胞总数和皮质酮水平不受禁食时间的影响。结果表明,禁食时间长短能显著影响雌性长爪沙鼠的免疫功能,随禁食时间的延长,长爪沙鼠T细胞介导的免疫功能逐渐受抑制,这可能与体脂和葡萄糖含量下降有关,血清瘦素逐渐降低也可能是其免疫受抑制的原因。     

Suppression of collagen-induced arthritis in DBA/1J mice by preimmunization with house dust mite extract.

Collagen-induced arthritis (CIA) can be induced in DBA/1J mice by immunization with bovine type II collagen (bCII) and is a model of some types of human autoimmune rheumatoid arthritis. In this study we examined whether preimmunization of the mice with various antigens could inhibit the development of CIA. Preimmunization of the mice with an extract of the house dust mite Dermatophagoides farinae (mite antigen), chicken ovalbumin, or keyhole limpet hemocyanin strongly inhibited CIA development, but hen egg lysozyme, beta-lactoglobulin from bovine milk or myelin basic protein from guinea pig brain did not substantially affect CIA development. Splenic T cells and serum antibodies specific for mite antigen did not cross-react with bCII. Preimmunization of the mice with mite antigen did not affect the IFN-gamma and proliferative response of splenic T cells to bCII, nor serum antibody responses. The most inhibitory constituent had a molecular weight between 1,000 and 10,000.     

Investigation of the kynurenine pathway in Indoleamine 2, 3 dioxygenase deficient mice with inflammatory arthritis

Tryptophan is an essential amino acid involved in the protein synthesis, cognition, and immunity. Oxidative catabolism of tryptophan is executed by the sets of biochemical reactions collectively referred to as the kynurenine pathway. In the immune system, two distinct enzymes, Indoleamne 2,3 dioxygenase 1 (IDO1) and Indoleamine 2, 3 dioxygenase 2 (IDO2) can initiate metabolic flux through the kynurenine pathway. Rheumatoid arthritis is an autoimmune disease driven by the exacerbated immune response towards self antigens and characterized by the chronic inflammatory reaction of the diarthrodial joints. Collagen induced arthritis (CIA) is an animal model of rheumatoid arthritis. Using CIA in wild type (WT) and mice deficient with Indoleamine 2,3 dioxygenase (Ido1KO), it was of interest to test the impact of Ido1 deletion on the concentration of tryptophan and its catabolites as well as on mRNA expression for other genes on the kynurenine pathway. Here, when compared with samples taken from naïve WT animals and those with CIA, it was found that only in the inguinal lymph nodes (iLN) taken from Ido1KO mice with CIA tryptophan concentration was significantly increased. In contrast, mRNA expression for Ido2 was decreased in naïve as well as in the diseased iLN taken from Ido1KO mice. Deletion of Ido1 and reduced mRNA expression for Ido2 neither affected the concentration of the downstream metabolites of tryptophan nor mRNA expression for downstream genes on the kynurenine pathway in iLN. Moreover, the concentration of kynurenine in sera of mice with CIA was significantly decreased in Ido1KO mice with arthritis.