Isolation of HLA-DR-naturally presented peptides identifies T-cell epitopes for rheumatoid arthritis.

OBJECTIVE: Rheumatoid arthritis (RA) immunopathogenesis revolves around the presentation of poorly characterised self-peptides by human leucocyte antigen (HLA)-class II molecules on the surface of antigen-presenting cells to autoreactive CD4 +T cells. Here, we analysed the HLA-DR-associated peptidome of synovial tissue (ST) and of dendritic cells (DCs) pulsed with synovial fluid (SF) or ST, to identify potential T-cell epitopes for RA. METHODS: HLA-DR/peptide complexes were isolated from RA ST samples (n=3) and monocyte-derived DCs, generated from healthy donors carrying RA-associated shared epitope positive HLA-DR molecules and pulsed with RA SF (n=7) or ST (n=2). Peptide sequencing was performed by high-resolution mass spectrometry. The immunostimulatory capacity of selected peptides was evaluated on peripheral blood mononuclear cells from patients with RA (n=29) and healthy subjects (n=12) by flow cytometry. RESULTS: We identified between 103 and 888 HLA-DR-naturally presented peptides per sample. We selected 37 native and six citrullinated (cit)-peptides for stimulation assays. Six of these peptides increased the expression of CD40L on CD4 +T cells patients with RA, and specifically triggered IFN-γ expression on RA CD4 +T cells compared with healthy subjects. Finally, the frequency of IFN-γ-producing CD4 +T cells specific for a myeloperoxidase-derived peptide showed a positive correlation with disease activity. CONCLUSIONS: We significantly expanded the peptide repertoire presented by HLA-DR molecules in a physiologically relevant context, identifying six new epitopes recognised by CD4 +T cells from patients with RA. This information is important for a better understanding of the disease immunopathology, as well as for designing tolerising antigen-specific immunotherapies.

Immunosuppressive Mechanisms of Regulatory B Cells.

Regulatory B cells (Bregs) is a term that encompasses all B cells that act to suppress immune responses. Bregs contribute to the maintenance of tolerance, limiting ongoing immune responses and reestablishing immune homeostasis. The important role of Bregs in restraining the pathology associated with exacerbated inflammatory responses in autoimmunity and graft rejection has been consistently demonstrated, while more recent studies have suggested a role for this population in other immune-related conditions, such as infections, allergy, cancer, and chronic metabolic diseases. Initial studies identified IL-10 as the hallmark of Breg function; nevertheless, the past decade has seen the discovery of other molecules utilized by human and murine B cells to regulate immune responses. This new arsenal includes other anti-inflammatory cytokines such IL-35 and TGF-ß, as well as cell surface proteins like CD1d and PD-L1. In this review, we examine the main suppressive mechanisms employed by these novel Breg populations. We also discuss recent evidence that helps to unravel previously unknown aspects of the phenotype, development, activation, and function of IL-10-producing Bregs, incorporating an overview on those questions that remain obscure.

Regulation of Tolerogenic Features on Dexamethasone-Modulated MPLA-Activated Dendritic Cells by MYC.

The potential of tolerogenic dendritic cells (tolDCs) to shape immune responses and restore tolerance has turn them into a promising therapeutic tool for cellular therapies directed toward immune regulation in autoimmunity. Although the cellular mechanisms by which these cells can exert their regulatory function are well-known, the mechanisms driving their differentiation and function are still poorly known, and the variety of stimuli and protocols applied to differentiate DCs toward a tolerogenic phenotype makes it even more complex to underpin the molecular features involved in their function. Through transcriptional profiling analysis of monocyte-derived tolDCs modulated with dexamethasone (Dex) and activated with monophosphoryl lipid A (MPLA), known as DM-DCs, we were able to identify MYC as one of the transcriptional regulators of several genes differentially expressed on DM-DCs compared to MPLA-matured DCs (M-DCs) and untreated/immature DCs (DCs) as revealed by Ingenuity Pathway Analysis (IPA) upstream regulators evaluation. Additionally, MYC was also amidst the most upregulated genes in DM-DCs, finding that was confirmed at a transcriptional as well as at a protein level. Blockade of transactivation of MYC target genes led to the downregulation of tolerance-related markers IDO1 and JAG1. MYC blockade also led to downregulation of PLZF and STAT3, transcription factors associated with immune regulation and inhibition of DC maturation, further supporting a role of MYC as an upstream regulator contributing to the regulatory phenotype of DM-DCs. On the other hand, we had previously shown that fatty acid oxidation, oxidative metabolism and zinc homeostasis are amongst the main biological functions represented in DM-DCs, and here we show that DM-DCs exhibit higher intracellular expression of ROS and Zinc compared to mature M-DCs and DCs. Taken together, these findings suggest that the regulatory profile of DM-DCs is partly shaped by the effect of the transcriptional regulation of tolerance-inducing genes by MYC and the modulation of oxidative metabolic processes and signaling mediators such as Zinc and ROS.

Dexamethasone and Monophosphoryl Lipid A Induce a Distinctive Profile on Monocyte-Derived Dendritic Cells through Transcriptional Modulation of Genes Associated With Essential Processes of the Immune Response.

There is growing interest in the use of tolerogenic dendritic cells (tolDCs) as a potential target for immunotherapy. However, the molecular bases that drive the differentiation of monocyte-derived DCs (moDCs) toward a tolerogenic state are still poorly understood. Here, we studied the transcriptional profile of moDCs from healthy subjects, modulated with dexamethasone (Dex) and activated with monophosphoryl lipid A (MPLA), referred to as Dex-modulated and MPLA-activated DCs (DM-DCs), as an approach to identify molecular regulators and pathways associated with the induction of tolerogenic properties in tolDCs. We found that DM-DCs exhibit a distinctive transcriptional profile compared to untreated (DCs) and MPLA-matured DCs. Differentially expressed genes downregulated by DM included MMP12, CD1c, IL-1B, and FCER1A involved in DC maturation/inflammation and genes upregulated by DM included JAG1, MERTK, IL-10, and IDO1 involved in tolerance. Genes related to chemotactic responses, cell-to-cell signaling and interaction, fatty acid oxidation, metal homeostasis, and free radical scavenging were strongly enriched, predicting the activation of alternative metabolic processes than those driven by counterpart DCs. Furthermore, we identified a set of genes that were regulated exclusively by the combined action of Dex and MPLA, which are mainly involved in the control of zinc homeostasis and reactive oxygen species production. These data further support the important role of metabolic processes on the control of the DC-driven regulatory immune response. Thus, Dex and MPLA treatments modify gene expression in moDCs by inducing a particular transcriptional profile characterized by the activation of tolerance-associated genes and suppression of the expression of inflammatory genes, conferring the potential to exert regulatory functions and immune response modulation.

TIM-1 defines a human regulatory B cell population that is altered in frequency and function in systemic sclerosis patients.

BACKGROUND: Systemic sclerosis (SSc) is a systemic autoimmune disease characterized by excessive production of extracellular matrix by fibroblasts on skin and internal organs. Although Th2 cells have been involved in fibroblast stimulation, hyperactivated B cells may also play an important role. Regulatory B cells (Bregs) are cells capable of inhibiting inflammatory responses and controlling autoimmune diseases. Although many Breg populations have in common the ability to produce high amounts of IL-10, a unique surface marker defining most human Bregs is lacking. It has been described in mice that T cell Ig and mucin domain protein 1 (TIM-1) is an inclusive marker for Bregs, and that TIM-1+ B cells are able to prevent the development of autoimmunity. The aim of this work was to evaluate TIM-1 as a marker for human IL-10+ Bregs, and to determine whether TIM-1+ B cells are defective in SSc patients. METHODS: SSc patients (n = 39) and 53 healthy subjects were recruited. TIM-1 and IL-10 expression was assessed in resting or activated peripheral blood CD19+ B cells by flow cytometry. The regulatory function of TIM-1+ or activated B cells from SSc patients and healthy subjects was assessed in autologous and allogenic co-cultures with CD4+ T cells, where T cell proliferation and IFN-γ, IL-17, TNF-α and IL-4 production by T cells was measured by flow cytometry. RESULTS: TIM-1 and IL-10 were preferentially expressed in transitional B cells, but were upregulated in naïve and memory B cells upon stimulation. The frequency of transitional TIM-1+ IL-10+ B cells was significantly decreased in SSc patients compared to healthy controls. In addition, activated B cells from SSc patients induced stronger allogenic Th1 and Th2 responses than activated B cells from healthy controls. Finally, TIM-1+ B cells, including transitional and non-transitional cells, exhibited a higher CD4+ T cell suppressive ability than TIM-1- B cells in healthy controls, but not in SSc patients. CONCLUSIONS: TIM-1 is a unique marker for the identification of a human IL-10+ Breg subpopulation which is partially superimposed with transitional B cells. Alterations in TIM-1+ B cells could contribute to the development of autoimmune diseases such as SSc.

Systemic Sclerosis Patients Present Alterations in the Expression of Molecules Involved in B-Cell Regulation.

The activation threshold of B cells is tightly regulated by an array of inhibitory and activator receptors in such a way that disturbances in their expression can lead to the appearance of autoimmunity. The aim of this study was to evaluate the expression of activating and inhibitory molecules involved in the modulation of B cell functions in transitional, naive, and memory B-cell subpopulations from systemic sclerosis patients. To achieve this, blood samples were drawn from 31 systemic sclerosis patients and 53 healthy individuals. Surface expression of CD86, MHC II, CD19, CD21, CD40, CD22, Siglec 10, CD35, and FcγRIIB was determined by flow cytometry. IL-10 production was evaluated by intracellular flow cytometry from isolated B cells. Soluble IL-6 and IL-10 levels were measured by ELISA from supernatants of stimulated B cells. Systemic sclerosis patients exhibit an increased frequency of transitional and naive B cells related to memory B cells compared with healthy controls. Transitional and naive B cells from patients express higher levels of CD86 and FcγRIIB than healthy donors. Also, B cells from patients show high expression of CD19 and CD40, whereas memory cells from systemic sclerosis patients show reduced expression of CD35. CD19 and CD35 expression levels associate with different autoantibody profiles. IL-10(+) B cells and secreted levels of IL-10 were markedly reduced in patients. In conclusion, systemic sclerosis patients show alterations in the expression of molecules involved in B-cell regulation. These abnormalities may be determinant in the B-cell hyperactivation observed in systemic sclerosis.

Dexamethasone preconditioning improves the response of collagen-induced arthritis to treatment with short-term lipopolysaccharide-stimulated collagen-loaded dendritic cells.

Background. Pharmacologically modulated dendritic cells (DCs) have been shown to restore tolerance in type II collagen-(CII-) induced arthritis (CIA). We examined the effect of dexamethasone (DXM) administration as a preconditioning agent, followed by an injection of lipopolysaccharide-(LPS-) stimulated and CII-loaded DCs on the CIA course. Methods. After CIA induction, mice pretreated with DXM were injected with 4-hour LPS-stimulated DCs loaded with CII (DXM/4hLPS/CII/DCs). Results. Mice injected with DXM/4hLPS/CII/DCs displayed significantly less severe clinical disease compared to animals receiving 4hLPS/CII/DCs alone or those in which only DXM was administered. Cytokine profile evaluation showed that CD4+ T cells from DXM/4hLPS/CII/DCs and 4hLPS/CII/DCs groups release higher IL-10 levels than those from mice receiving DXM alone or CIA mice. CD4+ T cells from all DC-treated groups showed less IL-17 release when compared to the CIA group. On the contrary, CD4+ T cells from DXM/4hLPS/CII/DCs and 4hLPS/CII/DCs groups released higher IFN- γ levels than those from CIA group. Conclusion. A combined treatment, including DXM preconditioning followed by an inoculation of short-term LPS-stimulated CII-loaded DCs, provides an improved strategy for attenuating CIA severity. Our results suggest that this benefit is driven by a modulation in the cytokine profile secreted by CD4+ T cells.

Blocking of p38 and transforming growth factor ß receptor pathways impairs the ability of tolerogenic dendritic cells to suppress murine arthritis.

OBJECTIVE: Dendritic cells (DCs) modulated with lipopolysaccharide (LPS) are able to reduce inflammation when therapeutically administered into mice with collagen-induced arthritis (CIA). The aim of this study was to uncover the mechanisms that define the tolerogenic effect of short-term LPS-modulated DCs on CIA. METHODS: Bone marrow-derived DCs were stimulated for 4 hours with LPS and characterized for their expression of maturation markers and their cytokine secretion profiles. Stimulated cells were treated with SB203580 or SB431542 to inhibit the p38 or transforming growth factor ß (TGFß) receptor pathway, respectively, or were left unmodified and, on day 35 after CIA induction, were used to inoculate mice. Disease severity was evaluated clinically. CD4+ T cell populations were counted in the spleen and lymph nodes from inoculated or untreated mice with CIA. CD4+ splenic T cells were transferred from mice with CIA treated with LPS-stimulated DCs or from untreated mice with CIA into other mice with CIA on day 35 of arthritis. RESULTS: Treatment with LPS-stimulated DCs increased the numbers of interleukin-10 (IL-10)-secreting and TGFß-secreting CD4+ T cells, but decreased the numbers of Th17 cells. Adoptive transfer of CD4+ T cells from treated mice with CIA reproduced the inhibition of active CIA accomplished with LPS-stimulated DCs. The therapeutic effect of LPS-stimulated DCs and their influence on T cell populations were abolished when the p38 and the TGFß receptor pathways were inhibited. CONCLUSION: DCs modulated short-term (4 hours) with LPS are able to confer a sustained cure in mice with established arthritis by re-educating the CD4+ T cell populations. This effect is dependent on the p38 and the TGFß receptor signaling pathways, which suggests the participation of IL-10 and TGFß in the recovery of tolerance.

Weak CD4+ T-cell responses to citrullinated vimentin in rheumatoid arthritis patients carrying HLA-DR9 alleles.

Citrullinated vimentin (cVIM) is one of the antigens specifically targeted by anti-citrullinated protein antibodies (ACPA) in rheumatoid arthritis (RA) patients. The association between ACPA and certain HLA-DRB1 alleles, those coding for the shared epitope (SE), suggests that this response could be T-cell mediated. HLA-DR9 alleles, which do not code for the SE, have recently been associated with ACPA (+) RA. The objective of this work was to study CD4+ T cell responses to cVIM in RA patients and healthy controls carrying HLA-DR9 alleles. Fourteen RA patients and ten healthy controls previously genotyped for HLA-DRB1 were studied for the presence of serum anti-cVIM antibodies by Western blot and ELISA. Peripheral blood mononuclear cells were stimulated with native vimentin and cVIM, and CD4+ T cells proliferation was assessed by flow cytometry. Citrulline-specific CD4+ T cells proliferation was found not only in RA patients but also in healthy controls. Although most patients carrying HLA-DR9 alleles present anti-cVIM antibodies, HLA-DR9 alleles were associated with weaker cVIM-driven CD4+ T-cell responses among RA patients. These results suggest that HLA-DR9 alleles could exert a protective effect on the recognition of cVIM epitopes by CD4+ T cells. In this context, other citrullinated proteins may break T and B cell tolerance, with cVIM only acting as a cross-reactive target for ACPA.

Anti-TNF therapy in patients with rheumatoid arthritis decreases Th1 and Th17 cell populations and expands IFN-γ-producing NK cell and regulatory T cell subsets.

The aim of this work was to study the effect of anti-TNF treatment on CD4+ Th1, Th17 and regulatory T cells (Tregs), together with CD8+ T cells and NK cells from rheumatoid arthritis (RA) patients. For this purpose, 18 RA patients received adalimumab during 16weeks and their peripheral blood lymphocytes were assessed by flow cytometry at the beginning and at the end of the study. We found that the proportion of Th17 cells was directly correlated with Th1 cells, but inversely correlated with IFN-γ-producing NK cells. A decrease was observed in Th1, Th17 cells and IFN-γ-producing CD8+ T cells by anti-TNF therapy. Conversely, the proportion of Tregs increased, as did the percentage of IFN-γ-producing NK cells. We postulate that a rise in IFN-γ production due to recovery of NK cells' function, together with expanded Tregs, contribute to decrease the Th17 response in anti-TNF-treated RA patients.

The presence of anti-citrullinated protein antibodies (ACPA) does not affect the clinical response to adalimumab in a group of RA patients with the tumor necrosis factor (TNF) α-308 G/G promoter polymorphism.

The introduction of antitumor necrosis factor (TNF) agents has improved the outcome for many patients with rheumatoid arthritis (RA). To date, the only replicated genetic predictor of anti-TNF response is the -308 G > A single-nucleotide polymorphism in the TNF promoter region. The presence of the -308 TNF G/G genotype appears to be a marker of good response to anti-TNF treatment. Anti-citrullinated protein antibodies (ACPA) have been linked with erosive disease, and have been established as the single most reliable prognostic factor in clinical practice. To test the hypothesis that the ACPA status may affect the -308 G/G patients rate of response to TNF blockade, we prospectively investigated a group of 52 RA patients with the -308 G/G genotype who were ACPA (+) or ACPA (-). All patients were treated with adalimumab, and the clinical response was studied using the Disease Activity Score in 28 joints (DAS28) at 24 weeks of treatment. Over 85% of patients were DAS28 responders in both groups. No significant differences were found between patients from both groups, according to the DAS28 criteria of response at week 24 (p = 0.79). In conclusion, our findings suggest that the ACPA status does not affect the clinical response to anti-TNF therapy in -308 TNF G/G patients.

B cells from rheumatoid arthritis patients show important alterations in the expression of CD86 and FcgammaRIIb, which are modulated by anti-tumor necrosis factor therapy.

INTRODUCTION: Several molecules help preserve peripheral B cell tolerance, but when altered, they may predispose to autoimmunity. This work studied the expression of the costimulatory molecule CD86 and the inhibitory receptor for IgG immune complexes FcgammaRIIb (CD32b), on B cells from rheumatoid arthritis (RA) patients, and the influence of anti-tumor necrosis factor (TNF) therapy. METHODS: Peripheral B cells from 18 RA patients and 13 healthy donors were characterized using flow cytometry. Eleven patients who underwent a six-month adalimumab therapy were further assessed for phenotypic changes on their B cells. RESULTS: RA patients exhibited a high percentage of naïve and memory B cells expressing CD86. In contrast, expression of FcgammaRIIb was significantly reduced on RA memory B cells and plasmablasts as compared to healthy donors, probably due to downregulation of this receptor when differentiating from naïve to memory cells. These alterations on FcgammaRIIb were associated with high levels of anti-citrullinated vimentin autoantibodies. In addition, treatment with adalimumab normalized the expression of CD86 on memory B cells and reduced the expression of FcgammaRIIb, mainly on naïve B cells. CONCLUSIONS: Our findings show that peripheral B cells from RA patients have an altered expression of key molecules, such as CD86 and FcgammaRIIb. Because this latter receptor is required for feedback inhibition, a deficient expression might contribute to humoral autoimmune responses. Furthermore, these molecules are likely to be influenced by inflammatory factors, since they were modulated by TNF inhibition.

Characterization of progressive periodontal lesions in chronic periodontitis patients: levels of chemokines, cytokines, matrix metalloproteinase-13, periodontal pathogens and inflammatory cells.

BACKGROUND AND AIMS: Periodontitis is an infection with an episodic nature of tissue support destruction. The aim of this work was to determine the levels of chemokines, cytokines, matrix metalloproteinase-13, periodontal pathogens and inflammatory cells in periodontal sites characterized by active periodontal connective tissue destruction. MATERIAL AND METHOD: Fifty-six patients with moderate or advanced severity of chronic periodontitis were selected. Periodontitis was characterized by at least six sites with probing depth > or =5 mm, clinical attachment level > or =3 mm and radiographic bone loss. Periodontitis progression was determined by the tolerance method. Receptor activator for nuclear factor kappa B-ligand (RANK-L), monocyte chemoattractant protein-1 (MCP-1), tumour necrosis factor-alpha (TNF-alpha), IL-1beta, MMP-13, Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Tannerella forsithia and inflammatory cells levels were determined. Statistical analysis was performed using the Stata 7.0 software. Data were expressed as mean+/-SD and paired samples t-test and chi(2) tests were used. RESULTS: Higher RANK-L, IL-1beta and MMP-13 activity levels were observed in active sites (p<0.05). The proportion of P. gingivalis, A. actinomycetemcomitans, T. forsythia and the number of CD4(+) T were higher in active than in inactive sites (p>0.05). CONCLUSION: The detection of periodontopathic bacteria, host matrix metalloproteinases and cytokines in periodontitis patients with lesions undergoing episodic attachment loss could partially explain the mechanisms associated with the destruction of the supporting tissues of the tooth.

Inflammation, synovial angiogenesis and chondroid apoptosis in the evolution of type II collagen-induced arthritis.

Using the murine model of type II collagen-induced arthritis (CIA), we studied its evolution over time by histopathological, immunohistochemical and clinical evaluations. The first clinical symptoms appeared 28 days post-inoculation (dpi), with bovine type II collagen, with an average arthritic index of 1.00 +/- 0.48 corresponding to erythema of the articulation. The disease progressed, and by 70 dpi showed an average arthritic index of 3.83 +/- 0.27 corresponding to edema and maximum deformation, with ankylosis. Computed morphometry demonstrated that, in comparison to controls, the induction of CIA, produces a significant and increasing accumulation of inflammatory cells, fibrosis (p < 0.0001) and cartilage destruction (p = 0.0029). Likewise, the area of von Willebrand factor (vWF) immunostaining, as an indicator of endothelial proliferation, increased significantly from 28 dpi (p < 0.0001), in CIA mice compared to controls. However, the effective synovial vascularization, calculated as the synovial vascular bed area index, significantly increased by 42 dpi (p = 0.0014). This indicates that the activation and proliferation of endothelium becomes significant before an effective vascularization area is formed. The apoptosis index was also an earlier indicator of cartilage damage, becoming significant from 28 dpi in comparison to controls (p < 0.0001). Finally, it was observed that the increase in the arthritic index showed a strong correlation with the increase in both angiogenesis (r = 0.95; p = 0.0021) and apoptosis (r = 0.90; p = 0.0015). In conclusion, a robust correlation between synovial membrane inflammation, angiogenesis and chondrocyte apoptosis, with respect to the increase in the clinical severity of CIA, has been demonstrated by a quantitative computer-assisted immunomorphometric analysis.

Short-term lipopolysaccharide stimulation induces differentiation of murine bone marrow-derived dendritic cells into a tolerogenic phenotype.

Dendritic cells (DCs) are professional, antigen-presenting cells, which induce and regulate T cell reactivity. DCs are crucial in innate and adaptive immune responses, and are also involved in central and peripheral tolerance induction. Tolerance can be mediated by immature and semi-mature DCs expressing low levels of co-stimulator and major histocompatibility complex (MHC) molecules. The aim of this study was to investigate the ability of short-term lipopolysaccharide (LPS) stimulation to modulate the stage of differentiation of bone marrow-derived DCs. For this purpose, DCs obtained from DBA1/lacJ mice were stimulated for four (4hLPS/DCs) or 24 (24hLPS/DCs) hours with LPS, using DCs without stimulation (0hLPS/DCs) as a control. Flow cytometry analysis of 4hLPS/DCs showed intermediate CD40 and MHC class II expression, lower than that of 24hLPS/DCs (fully mature), and greater than that of 0hLPS/DCs (immature). A functional assay showed that 4hLPS/DCs displayed increased endocytotic ability compared to 24hLPS/DCs, indicating a semi-mature state. 4hLPS/DCs were greater producers of IL-10 protein and TGFbeta1 mRNA than 24hLPS/DCs and immature DCs, displaying a cytokine production pattern that is characteristic of tolerogenic DCs. An assay for antigen-presenting capacity demonstrated that 4hLPS/DCs induced secretion of IL-2 from an OTH4 T cell hybridoma, indicating a functional presenting activity. Finally, the tolerogenic phenotype of 4hLPS/DCs was demonstrated by their ability to interfere with the progression of bovine type II collagen (bII)-induced arthritis (CIA) when they were loaded with bCII antigen and injected into mice with established CIA. We conclude that the stimulation of murine bone marrow-derived DCs with LPS for four hours generates semi-mature DCs with tolerogenic capability.

Could single-nucleotide polymorphisms (SNPs) affecting the tumour necrosis factor promoter be considered as part of rheumatoid arthritis evolution?

Tumour necrosis factor (TNF), a cytokine mainly produced by macrophages, is associated with a broad spectrum of biological effects, mainly associated with the host defense against microbes. The TNF gene is located on chromosome six within the major histocompatibility complex (MHC). Rheumatoid arthritis (RA) is a systemic autoimmune disease where TNF plays a central role in its etiology and pathogenesis. Written medical evidence of RA can be traced at least as far back as the 17th century, while human paleopathological studies appear to show the presence of RA prior to this period. The fact that RA has experienced an increment both in severity and mortality could be explained by many causes, particularly the crucial role of the immune system. Single-nucleotide polymorphisms (SNPs) are the most common genetic variations and occur at a frequency of approximately 1 in 1000 bp throughout the genome. The -308 TNF SNP is a mutation that affects the promoter region of the TNF gene. It defines the TNF1 and TNF2 alleles, determining low and high levels of TNF expression, respectively. The presence of the TNF2 allele has also been linked to increased susceptibility to and severity in a variety of autoimmune and inflammatory disorders, including RA, systemic lupus erythematosus, and ankylosing spondylitis. Studies on the functional significance of -308 SNP have detected higher levels of TNF production by cells from TNF2-carrying individuals than cells from TNF1 individuals. This difference does not appear to be due to other genes lying within the MHC region. Since the presence of the TNF2 allele may increase the host's resistance to local infection, by increasing local production of TNF at the infection site, we may suggest that such a mutation has emerged as a selective advantage to carriers of the TNF2 allele. This hypothesis may prove itself by observing the high incidence of tuberculosis and other infectious processes in those patients treated with anti-TNF therapy. Since the human lifespan has increased, the persistence of the TNF2 allele at high frequency in the population now confers what appears to be a marked survival disadvantage. As a result of the disregulation of the immune system, the genetically-predisposed host expresses larger amounts of TNF, leading to chronic inflammatory processes and autoimmune diseases, currently more prevalent. We suggest that RA, a relatively new and increasingly frequent disease, is favored by the presence of the -308 TNF promoter polymorphism, responsible for increased TNF production.

[Emergent therapies for rheumatoid arthritis]. / Terapias emergentes en artritis reumatoide.

The use of biological agents such as etanercept, infliximab, adalimumab and anakinra has been recently approved for the treatment of rheumatoid arthritis. All are effective controlling signs and symptoms and inhibiting disease progression. To overcome the problems generated by their high costs and possible participation in reactivating latent infections, other therapeutic tools are being developed. Gene therapy using expression vectors carrying genes coding for specific proteins, may interfere in key points involved in the pathogenesis of the disease. Intra-articular administration of cDNA coding for soluble TNF receptors, IL-1, or IL-1Ra decreases signs of the disease in animal models. Vectors, expressing inhibitors of signal transduction pathways involving to NF-kB and JAK-STAT-3, are effective in modulating joint inflammation in mice. The use of antigen-pulsed antigen presenting cells or dendritic cells (DC) bound to apoptosis-inducing molecules, specifically eliminates autoreactive T cells. Other novel approach attempts the development of T regulatory-inducing tolerogenic DC-based vaccines that inhibit autoreactive T cells, through the secretion of suppressing cytokines or by other mechanisms to be elucidated. Oral tolerance induction to auto-antigens is also a successful experimental strategy under study. Current research aims to control peripheral tolerance in rheumatoid arthritis patients.

Multiple imputation procedures allow the rescue of missing data: an application to determine serum tumor necrosis factor (TNF) concentration values during the treatment of rheumatoid arthritis patients with anti-TNF therapy.

Longitudinal studies aimed at evaluating patients clinical response to specific therapeutic treatments are frequently summarized in incomplete datasets due to missing data. Multivariate statistical procedures use only complete cases, deleting any case with missing data. MI and MIANALYZE procedures of the SAS software perform multiple imputations based on the Markov Chain Monte Carlo method to replace each missing value with a plausible value and to evaluate the efficiency of such missing data treatment. The objective of this work was to compare the evaluation of differences in the increase of serum TNF concentrations depending on the -308 TNF promoter genotype of rheumatoid arthritis (RA) patients receiving anti-TNF therapy with and without multiple imputations of missing data based on mixed models for repeated measures. Our results indicate that the relative efficiency of our multiple imputation model is greater than 98% and that the related inference was significant (p-value < 0.001). We established that under both approaches serum TNF levels in RA patients bearing the G/A -308 TNF promoter genotype displayed a significantly (p-value < 0.0001) increased ability to produce TNF over time than the G/G patient group, as they received successively doses of anti-TNF therapy.

Multiple imputation procedures allow the rescue of missing data: An application to determine serum tumor necrosis factor (TNF) concentration values during the treatment of rheumatoid arthritis patients with anti-TNF therapy

Longitudinal studies aimed at evaluating patients clinical response to specific therapeutic treatments are frequently summarized in incomplete datasets due to missing data. Multivariate statistical procedures use only complete cases, deleting any case with missing data. MI and MIANALYZE procedures of the SAS software perform multiple imputations based on the Markov Chain Monte Carlo method to replace each missing value with a plausible value and to evaluate the efficiency of such missing data treatment. The objective of this work was to compare the evaluation of differences in the increase of serum TNF concentrations depending on the ¡308 TNF promoter genotype of rheumatoid arthritis (RA) patients receiving anti-TNF therapy with and without multiple imputations of missing data based on mixed models for repeated measures. Our results indicate that the relative efficiency of our multiple imputation model is greater than 98 percent and that the related inference was significant (p-value < 0.001). We established that under both approaches serum TNF levels in RA patients bearing the G/A ¡308 TNF promoter genotype displayed a significantly (p-value < 0.0001) increased ability to produce TNF over time than the G/G patient group, as they received successively doses of anti-TNF therapy.

The -308 polymorphism in the promoter region of the tumor necrosis factor-alpha (TNF-alpha) gene and ex vivo lipopolysaccharide-induced TNF-alpha expression in patients with aggressive periodontitis and/or type 1 diabetes mellitus.

Several single-nucleotide polymorphisms (SNPs) have been identified in the TNF-alpha gene promoter. The transition G-->A at position -308 generates the TNF-alpha1 (G/G) and TNF-alpha2 (G/A or A/A) alleles, where the polymorphic TNF-alpha2 allele is associated with a high, in vitro TNF-alpha expression and an increased susceptibility to diverse illnesses. Here we study the association of the -308 TNF-alpha SNP with the susceptibility for developing aggressive periodontitis (AP), AP combined with type 1 diabetes mellitus (DM) and DM. We also explore the TNF-alpha capability expression and the presence of the -308 polymorphism. For this purpose we recruited 27 individuals with AP (AP+ group), 27 individuals with AP combined with DM (AP+/DM+ group), and 27 individuals with DM without signs of periodontitis upon clinical examination (DM+ group). The control group was comprised of 30 subjects. Genotyping for TNF-alpha promoter was performed by PCR-RFLP analysis. For TNF-alpha expression we used a blood culture system.