Gabriela Franco Salinas

Anti-TNF treatment blocks the induction of T cell-dependent humoral responses

Objective Experimental and human data suggest that tumour necrosis factor (TNF) blockade may affect B cell responses, in particular the induction of T cell-dependent (TD) humoral immunity. This study aimed to assess this hypothesis directly in patients with arthritis by analysing longitudinally the effect of TNF blockade on B cell activation and the maturation of humoral responses against TD and T cell-independent vaccines. Materials and methods Peripheral blood samples were obtained from 56 spondyloarthritis patients before and after treatment with either non-steroidal anti-inflammatory drug (NSAID) alone or TNF blockers and analysed for B cell activation, plasma cell differentiation, germinal centre versus extra-follicular B cell maturation, and somatic hypermutation. Vaccine responses to hepatitis B and Streptococcus pneumoniae were measured by ELISA. Results TNF blockade augmented B cell activation as reflected by the expression of early activation markers, CD40, and costimulatory molecules, without affecting differentiation towards plasmablasts. This was associated with a specific increase of the unswitched fraction of circulating memory B cells and a decreased level of somatic hypermutation in anti-TNF treated patients, indicating an impairment of the germinal centre-dependent B cell maturation. In agreement with these findings, TNF blockade profoundly suppressed the response to the TD vaccination against hepatitis B, whereas the T cell-independent response against pneumococcal polysaccharides was only modestly affected. Conclusions These data indicate that TNF blockade severely impedes the induction of primary TD humoral responses, probably by interfering with the germinal centre reaction.

Alterations of the synovial T cell repertoire in anti-citrullinated protein antibody-positive rheumatoid arthritis.

OBJECTIVE The association of HLA-DRB1 alleles with anti-citrullinated protein antibodies (ACPAs) in rheumatoid arthritis (RA) suggests the potential involvement of T lymphocytes in ACPA-seropositive disease. The purpose of this study was to investigate this hypothesis by systematic histologic and molecular analyses of synovial T cells in ACPA+ versus ACPA- RA patients. METHODS Synovial biopsy samples were obtained from 158 RA patients. Inflammation was determined histologically and immunohistochemically. RNA was extracted from peripheral blood mononuclear cells and synovial tissues obtained from 11 ACPA+ RA patients, 7 ACPA- RA patients, and 10 spondylarthritis (SpA) patients (arthritis controls). T lymphocyte clonality was studied by combined quantitative and qualitative T cell receptor CDR3 length distribution (LD) analysis and direct sequencing analysis. RESULTS ACPA+ and ACPA- RA patients were similar at both the clinical and histologic levels. At the molecular level, however, patients with ACPA+ synovitis displayed a marked elevation of qualitative CDR3 LD alterations as compared with those with ACPA- synovitis and with the SpA controls. These differences in CDR3 LD were not observed in the peripheral blood, indicating a selective recruitment and/or local expansion of T cells in the synovial compartment. The CDR3 LD alterations reflected true monoclonal or oligoclonal expansions, as confirmed by direct sequencing of the T cell receptor. The CDR3 LD alterations in RA synovium did not correlate with B cell clonal expansions but were inversely associated with synovial lymphoid neogenesis. CONCLUSION The T cell repertoire is specifically restricted in RA patients with ACPA+ synovitis. Whereas the origin and role of these clonal alterations remain to be determined, our data suggest the preferential involvement of T lymphocytes in ACPA-seropositive RA.

The role of B lymphocytes in the progression from autoimmunity to autoimmune disease

Autoimmunity, defined as the presence of autoreactive T and/or B lymphocytes in the periphery, is a frequent and probably even physiological condition. It is mainly caused by the fact that the central tolerance mechanisms, which are responsible for counter-selection of autoreactive lymphocytes, are not perfect and thus a limited number of these autoreactive cells can mature and enter the periphery. Nonetheless, autoreactive cells do not lead automatically to autoimmune disease as evidenced by a multitude of experimental and human data sets. Interestingly, the progression from autoimmunity to autoimmune disease is not only determined by the degree of central tolerance leakage and thus the amount of autoreactive lymphocytes in the periphery, but also by peripheral mechanism of activation and control of the autoreactive cells. In this review, we discuss the contribution of peripheral B lymphocytes in this process, ranging from activation of T cells and epitope spreading to control of the autoimmune process by regulatory mechanisms. We also discuss the parallels with the role of B cells in the induction and control of alloimmunity in the context of organ transplantation, as more precise knowledge of the pathogenic antigens and time of initiation of the immune response in allo- versus auto-immunity allows better dissection of the exact role of B cells. Since peripheral mechanisms may be easier to modulate than central tolerance, a more thorough understanding of the role of peripheral B cells in the progression from autoimmunity to autoimmune disease may open new avenues for treatment and prevention of autoimmune disorders.

The TNF family member APRIL dampens collagen-induced arthritis

Background The tumour necrosis factor (TNF)-family members B cell activating factor (BAFF) and A PRoliferation-Inducing Ligand (APRIL) play important roles in B cell biology, and share binding to B cell maturation antigen and transmembrane activator and cyclophilin ligand interactor, both receptors of the TNF-family. However, while it is reported that BAFF can break B cell tolerance, the role of APRIL in autoimmunity remains elusive. Objective To evaluate the role of APRIL on collagen-induced arthritis (CIA). Methods CIA was induced in APRIL-transgenic (Tg) DBA/1 mice and littermates. Disease progression was evaluated by clinical and histological signs of arthritis. In another experimental setting mice were exposed to the collagen antibody-induced arthritis. In addition, we tested T cell dependent humoral responses in APRIL-Tg mice. Results We found that APRIL-Tg displayed a strongly reduced incidence and severity of CIA compared with littermates, with decreases in collagen-specific autoantibody titres, immune complex deposition and downstream mast cell activation in joints. Notably, ectopic APRIL-expression was also found to negatively regulate T cell dependent humoral responses. The lower autoantibody production in APRIL-Tg mice during CIA appears to be crucial, as arthritis induced by administration of anti-collagen antibodies developed similar in APRIL-Tg and control mice, thus demonstrating that the downstream effector pathways induced by anti-collagen antibodies remain intact in APRIL-Tg mice. This protective effect was specifically mediated by APRIL, as adenoviral delivery of APRIL decreased CIA in a therapeutic setting. Conclusions Collectively, our data identify APRIL as a negative regulator of CIA by regulating autoantibody production. These findings are of important clinical relevance, as the therapeutic potential of transmembrane activator and cyclophilin ligand interactor-Fc (atacicept) is presently evaluated in clinical trials.

Sustained Rap1 activation in autoantigen-specific T lymphocytes attenuates experimental autoimmune encephalomyelitis.

Altered Ras superfamily guanine nucleotide triphosphatase signaling may contribute to the activation of autoreactive T cells in diseases such as rheumatoid arthritis and systemic lupus erythematosus. Here, we show that transgenic expression of activated Rap1, a Ras-related protein which is protective in murine arthritis, in both wildtype (WT) and 2D2 mice, enhances autoreactive T cell activation by myelin oligodendrocyte glycoprotein peptide in vitro and in vivo. However, RapV12 reduces the number of autoreactive T cells in both WT and 2D2 mice, and increases murine survival in experimental autoimmune encephalitis, suggesting Rap1 activation restricts autoimmune T cell-mediated pathology through enhancing tolerance.

The TNF-ligand APRIL can control CIA by regulating antibody-production and stimulating anti-inflammatory IL-10 producing B cells

Background Increased levels of the tumour necrosis factor (TNF) -ligand APRIL (A Proliferation Inducing Ligand) were found in synovial fluid and serum of patients with inflammatory arthritis pointing to a pro-inflammatory role of APRIL. APRIL can bind to BCMA and TACI, two receptors of the TNF family, which can also bind the B cell activating factor (BAFF). In the collagen-induced arthritis (CIA), administration of TACI-Ig was found to prevent disease progression and to lower disease scores, compared with controls. As TACI binds both APRIL and BAFF, it remained to be determined, whether this effect was due to the capacity of TACI to block just one or both ligands. Methods CIA was induced in APRIL-transgenic (Tg) DBA/1 mice and littermates. Severity of disease was scored for each paw using a scale 0–4. In addition, mice were analysed for histological signs of arthritis. Anticollagen antibody titers were determined by ELISA. Lymphocyte populations in draining lymph nodes, spleen and peritoneum were analysed by FACS. In another experimental setting mice were exposed to the collagen antibodies induced arthritis (CAIA). In addition, we employed models fort contact hypersensitivity (CHS) and experimental autoimmune encephalomyelitis (EAE). For the former, APRIL Tg and control mice were sensitised and challenged at the ear with oxazolone. EAE was induced by immunising mice with MOG, a myelin peptide, in adjuvant. Results APRIL Tg mice displayed in contrast to littermates a lower disease score and incidence of arthritis, and also produced less collagen specific antibodies. Joints of littermates had higher IgG levels and increased number of degranulating, thus activated, mast cells. To confirm that the decreased IgG levels developed in the CIA model in APRIL Tg mice are directly linked to the less severe disease development, we employed the model of CAIA. In fact, disease development in CAIA was similar in APRIL Tg and control mice. In addition, we detected a significantly increased IL-10 production of peritoneal B cells in APRIL Tg mice in the CIA model. Evidence is accumulating that IL-10 producing B cells can regulate autoimmune diseases including arthritis. The regulatory role of APRIL by modulating activity IL-10-producing B was confirmed in the CHS and EAE model. Conclusion Our results show that APRIL can control inflammation in the three tested disease models CIA, CHS and EAE. This suggests a therapeutic potential of APRIL agonists to downregulate inflammatory diseases such as rheumatoid arthritis.

TNFα blockade impairs T cell dependent humoural responses

Tumour necrosis factor α (TNFα) blockade in spondyloarthritis (SpA) induces antibodies specific for double stranded DNA, which is a T cell independent (TI) antigen. As these antibodies were restricted to the IgM isotype and no antibodies to T cell dependent (TD) antigens were induced, we investigated here if TNF blockade impairs the induction and maturation of TD humoural responses. 30 SpA patients (20 treated …