Agapitos Patakas

Interleukin 27 attenuates collagen-induced arthritis

Objective: To investigate the potential role of interleukin (IL) 27 in rheumatoid arthritis (RA) by examining the expression of IL27 in the articular joints of patients with RA and the effect of recombinant IL27 in vivo in a murine model of collagen-induced arthritis (CIA). Methods: Synovial membranes from patients with RA were examined for the presence of IL27 by immunohistochemistry and by western blot. Mice developing CIA were treated with IL27 and the ensuing disease progression and immunological profile determined. The effect of IL27 on T-cell response in vitro was also ascertained. Results: IL27 was clearly detected in the RA synovial membranes. Short-term administration of IL27 at the onset of the disease significantly attenuated disease severity compared with untreated controls. Histological examination showed that while untreated mice developed severe cellular infiltration in the joints, synovial hyperplasia and joint erosion, this pathology was profoundly reduced in IL27-treated animals. Treatment of mice with IL27 also decreased the amounts of serum IL6 and collagen-specific IgG2a. Spleen and lymph node cells from the IL27-treated mice produced significantly less interferon γ and IL17 than cells from the control mice when cultured with collagen in vitro. Conclusion: These results demonstrate that IL27 may be a potential therapeutic agent against RA at the onset of the disease.

Abatacept Limits Breach of Self-Tolerance in a Murine Model of Arthritis via Effects on the Generation of T Follicular Helper Cells

Abatacept modulates CD28-mediated T cell costimulation and is efficacious in the treatment of rheumatoid arthritis (RA). Its mechanism of action has not been fully elucidated but will likely reveal critical pathologic pathways in RA. We show that abatacept substantially modulated Ag-specific T and B cell responses in vivo. Ag-specific T cell proliferation was reduced, and the acquisition of an activated phenotype, characterized by upregulation of CD69, OX40, ICOS, and programmed death-1 and downregulation of CD62L, was suppressed. Furthermore, abatacept suppressed the production of inflammatory cytokines, such as IFN-γ and IL-17. These effects were associated with a failure of Ag-specific T cells to acquire the CXCR5+ICOS+ T follicular helper cell phenotype. This, in turn, led to a failure of these cells to enter B cell follicles, resulting in reduced specific Ab responses, despite normal B cell clonal expansion. To test the pathologic significance of this, we used a novel model of RA associated with breach of self-tolerance to self-Ag and demonstrated that abatacept prevented the emergence of self-reactivity. Thus, CD28-dependent signaling is required for optimal T follicular helper cell maturation and expansion, and its inhibition prevents loss of self-tolerance in a model of articular pathology. Thus, we provide a novel mode of action for abatacept with profound implications for its potential usefulness in early inflammatory arthropathies associated with autoantibody expression.

Identifying the Cells Breaching Self-Tolerance in Autoimmunity

Activation of auto-reactive T cells by activated dendritic cells (DCs) presenting self-Ag is widely assumed to be the precipitating event in the development of autoimmune disease. However, despite such widely held preconceptions, supporting data are scarce and subjective, particularly in experimental arthropathy. We have adapted a novel murine model of breach of self-tolerance allowing evaluation of the contribution of endogenous DCs to the development of autoimmune responses and disease. For the first time, we reveal the critical role played by conventional DCs, and the timing and location of this process. We further demonstrate the importance of this finding by clinically relevant, therapeutic manipulation of conventional DC function, resulting in decreased autoimmune phenotype and disease severity.

Antigen presentation kinetics control T cell/dendritic cell interactions and follicular helper T cell generation in vivo

The production of high affinity, class switched antibodies produced by B cells hinges on the effective differentiation of T follicular helper (Tfh) cells. Here we define conditions specifically enhancing Tfh differentiation and providing protection in a model of influenza infection. Tfh responses were associated with prolonged antigen presentation by dendritic cells (DCs), which maintained T cell/DC interactions into stage 3 (>72 hr) of activation. Blocking stage 3 interactions ablated Tfh generation, demonstrating a causal link between T cell-DC behaviour and functional outcomes. The current data therefore explain how duration of antigen presentation affects the dynamics of T cell-DC interactions and consequently determine Tfh cell differentiation in the developing immune response. DOI: http://dx.doi.org/10.7554/eLife.06994.001

Th17 Effector Cells Support B Cell Responses Outside of Germinal Centres

Th17 cells are pro-inflammatory CD4+T cells, which are important in immune responses against fungal pathogens and extracellular bacteria and have also been implicated in various autoimmune syndromes. However, their role in supporting B cell responses in these scenarios remains unclear, representing a significant lapse in our understanding of the role Th17 play in vaccine responses and the regulation of autoimmunity. We employed T cell and B cell receptor transgenic mice specific for model antigens, and adoptive transfer approaches that allowed the tracking of cognate B and T cells in situ and ex vivo using immunological methods. We have found that T cells activated under Th17 polarising conditions have a greater capacity to provide cognate B cell help compared with Th1 polarised populations, supporting higher expansion of antigen specific B cells and enhanced antibody titres. This advantage is associated with the increased persistence of Th17 polarised cells in areas of the lymph nodes where they can provide help (i.e. the B cell follicles). Also the Th17 cells are characterised by their higher expression of ICOS, a costimulatory molecule important for B cell help. Surprisingly, contrary to published reports, Th17 cells were not detected inside germinal centres, although they were found in close proximity to cognate B cells in the follicle early in the genesis of the humoral immune response. These data indicate that, Th17 cells have a more significant role earlier in the initiation/development of the germinal centre response and/or germinal centre-independent events, consistent with their early effector status.

Abatacept inhibition of T cell priming in mice by induction of a unique transcriptional profile that reduces their ability to activate antigen-presenting cells

To determine at the phenotypic, functional, and transcriptional levels whether abatacept, a CTLA‐4Ig molecule that binds with high affinity to CD80/86 on antigen‐presenting cells (APCs) and is used to treat rheumatoid arthritis, induces a state of immunologic tolerance in T cells and dendritic cells in mice.

Abatacept inhibits T cell priming by inducing of a unique transcriptional profile that reduces their ability to activate antigen presenting cells

To determine at the phenotypic, functional, and transcriptional levels whether abatacept, a CTLA‐4Ig molecule that binds with high affinity to CD80/86 on antigen‐presenting cells (APCs) and is used to treat rheumatoid arthritis, induces a state of immunologic tolerance in T cells and dendritic cells in mice.

Putative existence of reciprocal dialogue between Tfh and B cells and its impact on infectious and autoimmune disease

The evolution of the immune system to combat infectious disease is inextricably linked to the concomitant risk of autoimmunity. Central to the immune response in both scenarios is T cell-dependent antibody production. Thus, understanding the fundamentals of this process has important applications in both infectious and autoimmune or inflammatory disease. Recently, considerable attention has been paid to Tfh cells in this process both in terms of how they are generated and what role they play in antibody responses via their transit into the B cell follicle. However, there has been relatively little focus on what this mobilization to the follicle does for the Tfh cell. Thus in this article we review the current literature on Tfh cells in infection, autoimmunity and inflammatory disease and also highlight areas of controversy, with a particular focus on the potential importance of the follicular environment for T cell differentiation and function.

Arthritis in space and time - To boldly go!

Despite the profound impact of biologics on the treatment of rheumatoid arthritis (RA), long lasting disease remission remains elusive. We propose that this is a consequence of failing to target the right molecular pathway in the most relevant patient group at the appropriate time and place in disease progression. A limitation to testing this approach is the availability of disease models representing the discrete steps in autoimmune pathogenesis. A particular example is the paucity of models to dissect the conditions permissive for the breach of self‐tolerance, which would subsequently allow identification and testing of therapeutics for re‐establishment of self‐tolerance. We conclude that a detailed understanding of the location and timing of events leading to the systemic breach of self‐tolerance and subsequent progression to tissue specific pathology are required if rational application of existing drugs and identification of novel targets is to be achieved. This will take the personalised medicine revolution into the realms of contextualised medicine, whereby the right drug is targeted to the right tissue, in the right patient, at the right time.

Characterization of the anticollagen antibody response in a new model of chronic polyarthritis

OBJECTIVE Type II collagen (CII)-specific B cell responses have been recognized in human rheumatoid arthritis (RA) and in collagen-induced arthritis (CIA). An important limitation of the CIA model is that the CII response and the disease are stimulated by exogenously injected collagen. A model of experimental ovalbumin (OVA)-mediated acute arthritis has been established in which autoimmunity is spontaneous and elicited by antigen-specific T cells. This study was undertaken to create a new model of chronic autoimmune polyarthritis and characterize the associated CII-specific B cell response. METHODS Secondary challenge with OVA or CII in adjuvant was used to elicit chronic disease. CII-specific B cell responses against the epitopes U1, J1, C1, and citrullinated C1, together with the antibody affinity, were investigated in OVA-mediated arthritis. RESULTS Chronic autoimmune polyarthritis was induced and was dependent on the antigen used in the secondary challenge. U1 was the major CII epitope recognized, and antibodies showed the same affinity as those in CIA. CONCLUSION Our findings indicate that the development and severity of chronic disease is dependent on the antigen and is associated with an increased autoreactive B cell response directed against a specific CII epitope (U1). OVA-mediated chronic arthritis exhibits anti-CII antibodies (against U1), resembling human RA and murine CIA.