Short article: Absence of serological rheumatoid arthritis biomarkers in inflammatory bowel disease patients with arthropathies.

OBJECTIVE: Biomarkers that are associated with future progression to rheumatoid arthritis (RA) and joint destruction have been discovered previously in patients with arthralgia. The present study examined these RA biomarkers in inflammatory bowel disease (IBD) patients with arthropathies. PATIENTS AND METHODS: Sera from 155 IBD patients with and 99 IBD patients without arthropathies were analyzed for immunoglobulin (Ig) M rheumatoid factor (RF), IgA-RF, anti-cyclic citrullinated peptide 2, anti-cyclic citrullinated peptide 3.1, and anti-carbamylated protein antibody positivity using enzyme-linked immunosorbent assays. The prevalence of the autoantibodies in the IBD patients was compared with the prevalence in RA patients. RESULTS: No differences were found in biomarker positivity between IBD patients with and without arthropathies. Significantly more biomarker positivity (P<0.001) was observed in RA patients compared with IBD patients with arthropathies. Also, smoking turned out to be significantly associated with positivity for IgM-RF or IgA-RF. CONCLUSION: Our findings suggest that there is no apparent clinical value in the detection of RA biomarkers in serum of IBD patients to help identify arthropathies.

Anti-citrullinated protein antibodies contribute to platelet activation in rheumatoid arthritis.

INTRODUCTION: Although the role of platelets in rheumatoid arthritis (RA) is relatively unexplored, recent studies point towards a contribution of platelets in arthritis. We set out to determine platelet phenotype in RA and studied whether this could be influenced by the presence of anti-citrullinated protein antibodies (ACPA). METHODS: Platelets from healthy controls were incubated in the presence of plasma of patients with RA or age- and sex-matched healthy controls and plasma from ACPA(neg) or ACPA(pos) patients or in the presence of plate-bound ACPA. Characteristics of platelets isolated from patients with RA were correlated to disease activity. RESULTS: Platelets isolated from healthy controls displayed markers of platelet activation in the presence of plasma derived from RA patients, as determined by P-selectin expression, formation of aggregates and secretion of soluble CD40 ligand (sCD40L). Furthermore, levels of P-selectin expression and sCD40L release correlated with high ACPA titres. In accordance with these findings, enhanced platelet activation was observed after incubation with ACPA(pos) plasma versus ACPA(neg) plasma. Pre-incubation of platelets with blocking antibodies directed against low-affinity immunoglobulin G receptor (FcγRIIa) completely inhibited the ACPA-mediated activation. In addition, expression of P-selectin measured as number of platelets correlated with Disease Activity Score in 44 joints, C-reactive protein level, ACPA status and ACPA level. CONCLUSIONS: We show for the first time that ACPA can mediate an FcγRIIa-dependent activation of platelets. As ACPA can be detected several years before RA disease onset and activated platelets contribute to vascular permeability, these data implicate a possible role for ACPA-mediated activation of platelets in arthritis onset.

The interaction between HLA shared epitope alleles and smoking and its contribution to autoimmunity against several citrullinated antigens.

OBJECTIVE: Recent data suggest that a gene-environment interaction between smoking and the HLA shared epitope alleles plays a role in shaping the autoimmune reaction to specific citrullinated antigens. This study was undertaken to determine the effects of HLA shared epitope alleles and tobacco exposure on the immune response against various citrullinated antigens. These associations were analyzed in the anti-citrullinated protein antibody (ACPA)-positive stratum to control for the possibility that the associations found are explained by the known interaction between HLA shared epitope alleles and tobacco exposure on ACPA status. METHODS: In 661 patients with rheumatoid arthritis, reactivity against several citrullinated antigens from vimentin, fibrinogen, enolase, and myelin basic protein was determined by enzyme-linked immunosorbent assay. The effects of the HLA shared epitope alleles and tobacco exposure were assessed by logistic regression analysis. Biologic interaction was analyzed by investigating whether the effects of the risk factors combined exhibited departure from additivity. RESULTS: A significant interaction between tobacco exposure and HLA shared epitope alleles was found for the presence of ACPA as reported previously. When these interaction effects were studied for several ACPA "fine specificities," significant interactions were noted for several citrullinated peptides. However, these interactions were not present after stratification for ACPA status, indicating that the interaction between tobacco exposure and HLA shared epitope alleles influences autoimmunity not to specific citrullinated antigens, but rather to ACPA development. CONCLUSION: Our data indicate that the gene-environment interaction between HLA shared epitope alleles and smoking does not appear to shape the reactivity of the ACPA response. These data suggest that smoking promotes nonspecific citrullination rather than citrullination of specific antigens.

Immunohistochemical analysis as a means to predict responsiveness to rituximab treatment.

OBJECTIVE: Anti-CD20-mediated B cell depletion with rituximab is a new and effective therapy for rheumatoid arthritis (RA). Although B cells in peripheral blood (PB) are consistently depleted in all patients, the clinical effects are more heterogeneous, possibly related to differences in the depleting effects of lymphoid or solid tissues. The aim of this study was to investigate B cell depletion in different compartments (PB, bone marrow, and synovium) and determine predictive variables for responsiveness to rituximab therapy. METHODS: Before and 12 weeks after rituximab treatment, samples of PB, bone marrow, and synovium were collected from 25 patients with RA refractory to disease-modifying antirheumatic drugs and tumor necrosis factor-blocking agents. CD19+ and CD20+ B cells in PB and bone marrow were measured by flow cytometric analysis, whereas CD79a+ and cytoplasmic CD20+ B cells in the synovium were stained by immunohistochemistry. The effects of rituximab on serum Ig and autoantibodies were measured by enzyme-linked immunosorbent assay. RESULTS: Rituximab effectively depleted the CD20+ subset of B cells in the PB, bone marrow, and synovium of RA patients. Rituximab significantly reduced autoantibody production (anti-citrullinated protein antibodies [ACPAs] and rheumatoid factor [RF]), in part due to a nonspecific decrease in total Ig production. Importantly, positivity for circulating ACPA IgM, in combination with a high infiltration of CD79a+ B cells in the synovium, but not of CD138+ plasma cells, was a predictor of clinical outcome after rituximab treatment. ACPA IgM titers were independently associated with synovial infiltration of CD20-,CD79a+ B cells, but not with CD138+ plasma cells. CONCLUSION: These data provide novel insights into the mechanisms of CD20-mediated B cell depletion in the lymphoid and solid tissues of RA patients and suggest a pivotal role for ACPA IgM-producing plasmablasts in RA.