[Autoantibodies and the autoreactive immune response : There is more to ACPA than ACPA]. / Autoantikörper und die autoreaktive Immunantwort : ACPA sind mehr als nur ACPA.

The immune response against posttranslationally modified (PTM) antigens, in particular the generation of anti-citrullinated protein antibodies (ACPA), is a very specific hallmark of rheumatoid arthritis. The factors that initiate this immune response and the triggers that stimulate the transition from asymptomatic autoimmunity to autoimmune disease are so far unknown. Genetic risk factors and the maturation of the ACPA response prior to the onset of arthritis indicate an important role for helper T cells in this process. Antigens that trigger this process, however, remain to be defined. Notably, recent data demonstrate that ACPA do not only recognize citrullinated protein antigens. Other posttranslational protein modifications such as homocitrulline and acetyllysine are also recognized. This cross-reactivity towards different PTM antigens was found for various monoclonal ACPA and broadens the spectrum of antigens that can stimulate and activate ACPA-expressing B cells. Also, it suggests that such B cells could receive help from autoreactive but also from non-autoreactive T cells. This review summarizes these recent findings and provides insight into their potential relevance for the disease rheumatoid arthritis.

Antibodies and B cells recognising citrullinated proteins display a broad cross-reactivity towards other post-translational modifications.

OBJECTIVE: Autoantibodies against antigens carrying distinct post-translational modifications (PTMs), such as citrulline, homocitrulline or acetyllysine, are hallmarks of rheumatoid arthritis (RA). The relation between these anti-modified protein antibody (AMPA)-classes is poorly understood as is the ability of different PTM-antigens to activate B-cell receptors (BCRs) directed against citrullinated proteins (CP). Insights into the nature of PTMs able to activate such B cells are pivotal to understand the 'evolution' of the autoimmune response conceivable underlying the disease. Here, we investigated the cross-reactivity of monoclonal AMPA and the ability of different types of PTM-antigens to activate CP-reactive BCRs. METHODS: BCR sequences from B cells isolated using citrullinated or acetylated antigens were used to produce monoclonal antibodies (mAb) followed by a detailed analysis of their cross-reactivity towards PTM-antigens. Ramos B-cell transfectants expressing CP-reactive IgG BCRs were generated and their activation on stimulation with PTM-antigens investigated. RESULTS: Most mAbs were highly cross-reactive towards multiple PTMs, while no reactivity was observed to the unmodified controls. B cells carrying CP-reactive BCRs showed activation on stimulation with various types of PTM-antigens. CONCLUSIONS: Our study illustrates that AMPA exhibit a high cross-reactivity towards at least two PTMs indicating that their recognition pattern is not confined to one type of modification. Furthermore, our data show that CP-reactive B cells are not only activated by citrullinated, but also by carbamylated and/or acetylated antigens. These data are vital for the understanding of the breach of B-cell tolerance against PTM-antigens and the possible contribution of these antigens to RA-pathogenesis.

Effects of type II collagen epitope carbamylation and citrullination in human leucocyte antigen (HLA)-DR4(+) monozygotic twins discordant for rheumatoid arthritis.

The aim of this study is to investigate the effect of the native, citrullinated or carbamylated type II human collagen T cell- and B cell-epitopes on the adaptive immune response in rheumatoid arthritis (RA). Peripheral blood T and B cells obtained from a human leucocyte D4-related (antigen DR4(-) HLA-DR4)(+) woman with early RA, her healthy monozygotic twin and an unrelated HLA-DR3(+) woman with early RA were analysed for activation (CD154/CD69), apoptosis (annexin/7-aminoactinomycin), cytokine production [interferon (IFN)γ/interleukin (IL)-17/IL-4/IL-10/IL-6] and functional phenotype (CD45Ra/CCR7) after stimulation with the collagen native T cell epitope (T261-273), the K264 carbamylated T cell epitope (carT261-273), the native B cell epitope (B359-369) or the R360 citrullinated B cell epitope (citB359-369), and the combinations of these. The T cell memory compartment was activated by T cell epitopes in both discordant DR4(+) twins, but not in the DR3(+) RA. The collagen-specific activation of CD4(+) T cells was induced with both the native and carbamylated T cell epitopes only in the RA twin. Both T cell epitopes also induced IL-17 production in the RA twin, but a greater IL-4 and IL-10 response in the healthy twin. The citrullinated B cell epitope, particularly when combined with the carbamylated T cell epitope, induced B cell activation and an increased IL-6/IL-10 ratio in the RA twin compared to a greater IL-10 production in the healthy twin. Our data suggest that circulating collagen-specific T and B cells are found in HLA-DR4(+) subjects, but only RA activated cells express co-stimulatory molecules and produce proinflammatory cytokines. Carbamylation and citrullination further modulate the activation and cytokine polarization of T and B cells.

Does ex vivo CD34+ positive selection influence outcome after autologous hematopoietic stem cell transplantation in systemic sclerosis patients?

This EBMT Autoimmune Disease Working Party study aimed to evaluate the influence of CD34+ positive graft selection (CD34+) on the outcome of systemic sclerosis (SSc) patients after autologous hematopoietic stem cell transplantation (AHSCT). Clinical and laboratory data from 138 SSc patients at diagnosis, before and after AHSCT were retrospectively analyzed. CD34+ selection was performed in 47.1% (n=65) patients. By multivariate analysis adjusting for all factors differing between the two groups (without or with CD34+), there was no statistically significant difference in terms of overall survival (hazard ratio (HR): 0.98, 95% confidence interval (CI) 0.40-2.39, P=0.96), PFS (HR: 1.55, 95% CI 0.83-2.88, P=0.17) and incidence of relapse or progression (HR: 1.70, 95% CI 0.85-3.38, P=0.13). We demonstrate that CD34+ does not add benefit to the outcome of SSc patient treated with AHSCT. These findings should be further confirmed by prospective randomized trials.

How undifferentiated arthritis evolves into chronic arthritis.

Undifferentiated arthritis (UA) is a frequently occurring clinical presentation with a variable outcome. While some forms of UA will spontaneously remit, other forms will progress to chronic arthritis; an outcome that would preferably be prevented. Which immunological factors are normally at the basis of resolution of inflammation, and what, on the other hand, causes inflammation to persist? This review provides an overview of the immunological mechanisms involved in these two scenarios, including specific examples of how these mechanisms apply, or can be influenced in rheumatic diseases. Furthermore, what do we know about risk factors for chronic arthritis, such as the development of autoantibodies? The recent years have provided many insights concerning risk factors for autoantibody-positive versus autoantibody-negative rheumatoid arthritis, which are discussed along with a possible pathophysiological model incorporating autoantibodies into the larger process of disease development. Finally, the evolution of the autoantibody response over time is described.

[Biomarkers and personalized medicine]. / Biomarker und personalisierte Medizin.

Biomarkers form the basis for patient stratification and the development of individualized treatment strategies. As the understanding of the pathophysiological processes underlying rheumatic diseases increases, novel biomarkers will become available and established markers can be used more efficiently. Autoantibodies in rheumatoid arthritis (RA), for example, define a subgroup of patients with a specific risk profile and response to therapy. For this reason they have been added to the classification criteria for RA and are part of current treatment guidelines. In addition, novel markers are being evaluated and validated. For the concept of personalized medicine this indicates that the use of future therapeutic substances will be more frequently coupled to the detection of specific biomarkers. While this will decrease the number of patients who become eligible for certain treatments, it will increase efficacy and safety for patients and potentially the cost-effectiveness.

Toward a data-driven evaluation of the 2010 American College of Rheumatology/European League Against Rheumatism criteria for rheumatoid arthritis: is it sensible to look at levels of rheumatoid factor?

OBJECTIVE: Recently, new classification criteria for rheumatoid arthritis (RA) have been devised by methodology that used first a quantitative approach (data from databases), then a qualitative approach (consensus; based on paper patients), and finally a common sense-based approach (evaluation of the former phases). Now the individual items that make up these criteria are being evaluated. This study was undertaken to analyze the item "autoantibodies," in particular rheumatoid factor (RF) level. METHODS: Three separate cohorts comprising a total of 972 patients with undifferentiated arthritis were studied for RA development (according to the 1987 American College of Rheumatology criteria) and arthritis persistence. The positive predictive value (PPV), negative predictive value (NPV), and likelihood ratios (LRs) were compared between different levels of RF and the presence of anti-citrullinated protein antibody (ACPA). A similar comparison was made in 686 RA patients for the rate of joint destruction and achievement of sustained disease-modifying antirheumatic drug-free remission during 7 years of followup. The variation in RF levels obtained by different measurement methods in the same RF-positive sera was explored. RESULTS: Compared to high RF levels, presence of ACPA had a better balance between positive LR and negative LR and between PPV and NPV for RA development. The additive value of ACPA assessment after testing for RF level was higher than vice versa. The association between high RF level and RA severity was not as strong as that between ACPA antibodies and RA severity. The RF level obtained by different methods in the same patients' sera varied considerably. CONCLUSION: Our findings indicate that determination of RF level is subject to large variation; high RF level has limited additive prognostic value compared to ACPA positivity. Thus, omitting RF level and using RF presence, ACPA presence, and ACPA level may improve the 2010 criteria for RA.

Anti-citrullinated protein antibodies have a low avidity compared with antibodies against recall antigens.

OBJECTIVES: Anti-citrullinated protein antibodies (ACPA) are highly specific for rheumatoid arthritis (RA) and have been implicated in disease pathogenesis. Recent ongoing evidence indicates that the ACPA response broadens before precipitation of full-blown RA, as indicated by a more extensive isotype usage and an increased citrullinated epitope recognition profile. Nonetheless, the evolution of the ACPA response is still poorly understood and might intrinsically differ from the protective responses against pathogens. METHODS: The avidity and the avidity maturation of ACPA in relation to the avidity of antibodies against recall antigens were analysed. RESULTS: The avidity of ACPA was significantly lower than the avidity of antibodies to the recall antigens tetanus toxoid and diptheria toxoid. Moreover, ACPA did not show avidity maturation during longitudinal follow-up and ACPA avidity was also relatively low in patients who displayed extensive isotype switching. CONCLUSIONS: These observations indicate that the natural evolution of ACPA differs from the development of antibodies against recall antigens. These data also indicate that ACPA avidity maturation and isotype switching are disconnected, whereby extensive isotype switching occurs in the setting of restricted avidity maturation. Intrinsic differences between the RA-specific autoantibody system and protective antibody responses against pathogens could be of relevance for designing novel B cell-targeted therapies for RA.

[Polyarteritis nodosa - a "classical" case]. / Panarteritis nodosa - ein "klassischer" Fall.

Diagnosis of polyarteritis nodosa is often delayed due to the vast heterogeneity of initial clinical symptoms. The case presented shows the clinical image of the disease, leading from the first symptoms up to verification of the diagnosis by sural-nerve biopsy. We discuss the classification of the disease among other types of vasculitis, the classification criteria proposed by the American College of Rheumatology (ACR) as well as current therapeutic options. This case underlines the interdisciplinary character of the disease, challenging neurologists, dermatologists, rheumatologists and orthopedics alike.

[Rheumatology]. / Rheumatologie.

The advent of monoclonal antibodies for the treatment of rheumatic diseases has revolutionized our understanding of therapeutic efficacy. Only a few years ago, response rates of >70% combined with significant reductions in inflammatory activity and radiologic progression would have been impossible. At the same time, however, issues of safety and cost have gained in importance and challenge physicians and patients alike. Making these new drugs available to as many eligible patients as possible requires a thorough documentation of disease activity using standardized outcome measures as well as a profound knowledge of their safety profiles. In addition, institutional guidelines for the use of these agents need to be as close to the cutting edge of science as possible. The following article presents an overview of currently available biologic agents in rheumatology and a prospect of those to come.

The heat shock protein gp96 induces maturation of dendritic cells and down-regulation of its receptor.

Peptides associated with the heat shock protein gp96 induce a specific T cell response against cells from which gp96 is isolated. Recently, we have shown that gp96 binds to a yet unknown receptor present on dendritic cells (DC) and that receptor-mediated uptake is required for cross-presentation of gp96-associated peptides by DC. We now describe that gp96 mediates maturation of DC as determined by up-regulation of MHC class II and CD86 molecules, secretion of the cytokines IL-12 and TNF-alpha and enhanced T cell stimulatory capacity. Heat-denatured gp96 is not able to induce DC maturation and cytokine secretion. Furthermore, we show that mature DC are no longer able to bind gp96 molecules. Hence, the gp96 receptor is down-regulated on mature DC, suggesting that this receptor behaves similar to other receptors involved in antigen uptake like the scavenger receptor CD36, the mannose receptor or the integrins alpha(v)beta(3) and alpha(v)beta(5). Together, our findings provide an additional explanation for the remarkable immunogenicity of gp96 as a cross-priming antigen carrier and direct activator of DC.

The heat shock protein gp96: a receptor-targeted cross-priming carrier and activator of dendritic cells.

Heat shock proteins like gp96 (grp94) are able to induce specific cytotoxic T-cell (CTL) responses against cells from which they originate and are currently studied in clinical trials for use in immunotherapy of tumors. We have recently demonstrated that gp96 binds to at least one yet unidentified receptor restricted to antigen-presenting cells (APCs) like dendritic cells (DCs) but not to T cells. Moreover we have shown, that for CTL activation by gp96-chaperoned peptides receptor-mediated uptake of gp96 by APCs is required. Lately, we have discovered a second function of gp96 when interacting with professional APCs. Gp96 is able to mediate maturation of DCs as determined by upregulation of MHC class II, CD86 and CD83 molecules, secretion of pro-inflammatory cytokines IL-12 and TNF-alpha and enhanced T-cell simulatory capacity. Furthermore, the gp96 receptor(s) are down-regulated on mature DCs, suggesting that the gp96 receptor(s) behave similar to other endocytic receptors like CD36, mannose receptor etc. Our findings now provide additional evidence for the remarkable immunogenicity of gp96: first, the existence of specific gp96 receptors on APCs and second, the capacity to activate dendritic cells which is strictly required to enable these highly sophisticated APCs to prime CTL responses.