Expression of the beta6 integrin subunit is associated with sites of neutrophil influx in lung epithelium.

Inhalation of ozone by Rhesus monkeys results in epithelial injury and granulocyte influx in both conducting airways and respiratory bronchioles. We have reported that ozone-induced neutrophil recruitment and subsequent epithelial repair can be inhibited in vivo with a CD18 antibody. The antibody-mediated effect is abrogated by local instillation of C5a (a CD18-independent neutrophil chemoattractant), thereby demonstrating a role for neutrophils in lung epithelial repair processes. As an extension of this study, we examined the effect of ozone and neutrophil influx on epithelial expression of the beta6 integrin, an adhesion molecule associated with proliferation and repair. Expression of beta6 integrin was determined by immunohistochemistry for ozone-exposed monkeys treated with either control immunoglobulins or a CD18 antibody. The tracheal epithelium of ozone-exposed monkeys treated with control immunglobulins expressed the beta6 integrin. In contrast, the tracheal epithelium of ozone-exposed monkeys treated with CD18 antibody exhibited very low to undetectable expression of beta6 integrin. In association with C5a instillation and neutrophil influx, beta6 integrin was also observed in respiratory bronchiolar epithelium from both control and ozone-exposed animals. These findings cumulatively suggest that lung epithelial cell expression of beta6 integrin is associated with sites of neutrophil recruitment.     

Accelerated hand bone mineral density loss is associated with progressive joint damage in hands and feet in recent-onset rheumatoid arthritis

Introduction

To investigate whether accelerated hand bone mineral density (BMD) loss is associated with progressive joint damage in hands and feet in the first year of rheumatoid arthritis (RA) and whether it is an independent predictor of subsequent progressive total joint damage after 4 years.

Methods

In 256 recent-onset RA patients, baseline and 1-year hand BMD was measured in metacarpals 2-4 by digital X-ray radiogrammetry. Joint damage in hands and feet were scored in random order according to the Sharp-van der Heijde method at baseline and yearly up to 4 years.

Results

68% of the patients had accelerated hand BMD loss (>-0.003 g/cm²) in the first year of RA. Hand BMD loss was associated with progressive joint damage after 1 year both in hands and feet with odds ratios (OR) (95% confidence intervals [CI]) of 5.3 (1.3-20.9) and 3.1 (1.0-9.7). In univariate analysis, hand BMD loss in the first year was a predictor of subsequent progressive total joint damage after 4 years with an OR (95% CI) of 3.1 (1.3-7.6). Multivariate analysis showed that only progressive joint damage in the first year and anti-citrullinated protein antibody positivity were independent predictors of long-term progressive joint damage.

Conclusions

In the first year of RA, accelerated hand BMD loss is associated with progressive joint damage in both hands and feet. Hand BMD loss in the first year of recent-onset RA predicts subsequent progressive total joint damage, however not independent of progressive joint damage in the first year.     

L-selectin is required for fMLP- but not C5a-induced margination of neutrophils in pulmonary circulation

To study the role of L-selectin in neutrophil (PMN) margination and sequestration in the pulmonary microcirculation, maximally active concentrations of C5a (900 pmol/g) and N-formylmethionyl-leucyl-phenylalanine (fMLP; 0.34 pmol/g) were injected into the jugular vein of wild-type or L-selectin-deficient C57BL/6 mice. In wild-type mice administered C5a or fMLP, 92 +/- 1% and 34 +/- 9%, respectively, of peripheral blood PMN were trapped mostly in the pulmonary circulation as determined by immunohistochemistry and myeloperoxidase activity. In wild-type mice treated with F(ab')(2) fragments of the L-selectin monoclonal antibody MEL-14 or in L-selectin-deficient mice, C5a-induced neutropenia was not significantly reduced, but the decrease in peripheral PMN in response to fMLP was completely abolished, indicating that L-selectin is necessary for fMLP- but not C5a-induced pulmonary margination. Immunostained lung sections of fMLP- or C5a-treated mice showed sequestered neutrophils in alveolar capillaries with no evidence of neutrophil aggregates. We conclude that chemoattractant-induced PMN margination in the pulmonary circulation can occur by two separate mechanisms, one of which requires L-selectin.     

Intracellular control of human neutrophil secretion. I. C5a-induced stimulus-specific desensitization and the effects of cytochalasin B.

Human neutrophils released the granule constituents myeloperoxidase and lysozyme, but not the cytoplasmic enzyme lactic dehydrogenase, when pretreated with cytochalasin B and stimulated with purified human C5a. Prior exposure to C5a before the cytochalasin B, however, abrogated the subsequent secretory process. Interaction of neutrophils with C5a was shown to result in a concentration-dependent rapid desensitization that could not be overcome by later addition of cytochalasin B or of cytochalasin B and C5a. The effect was relatively stimulus specific in that neutrophils desensitized in this manner could be induced to release granule enzymes by casein or by complement-coated zymosan particles. Cytochalasin B effects on neutrophils appear to mimic those of surface binding of soluble stimuli such as C5a and immune complexes. It is suggested that desensitization in concert with surface stimulation may represent an important intracellular mechanism for limiting neutrophil secretion.     

A genetic variant in osteoprotegerin is associated with progression of joint destruction in rheumatoid arthritis

Introduction

Progression of joint destruction in rheumatoid arthritis (RA) is partly heritably; 45 to 58% of the variance in joint destruction is estimated to be explained by genetic factors. The binding of RANKL (Receptor Activator for Nuclear Factor κ B Ligand) to RANK results in the activation of TRAF6 (tumor necrosis factor (TNF) receptor associated factor-6), and osteoclast formation ultimately leading to enhanced bone resorption. This bone resorption is inhibited by osteoprotegerin (OPG) which prevents RANKL-RANK interactions. The OPG/RANK/RANKL/TRAF6 pathway plays an important role in bone remodeling. Therefore, we investigated whether genetic variants in OPG, RANK, RANKL and TRAF6 are associated with the rate of joint destruction in RA.

Methods

1,418 patients with 4,885 X-rays of hands and feet derived from four independent data-sets were studied. In each data-set the relative increase of the progression rate per year in the presence of a genotype was assessed. First, explorative analyses were performed on 600 RA-patients from Leiden. 109 SNPs, tagging OPG, RANK, RANKL and TRAF6, were tested. Single nucleotide polymorphisms (SNPs) significantly associated in phase-1 were genotyped in data-sets from Groningen (Netherlands), Sheffield (United Kingdom) and Lund (Switzerland). Data were summarized in an inverse weighted variance meta-analysis. Bonferonni correction for multiple testing was applied.

Results

We found that 33 SNPs were significantly associated with the rate of joint destruction in phase-1. In phase-2, six SNPs in OPG and four SNPs in RANK were associated with progression of joint destruction with P-value <0.05. In the meta-analyses of all four data-sets, RA-patients with the minor allele of OPG-rs1485305 expressed higher rates of joint destruction compared to patients without these risk variants (P = 2.35x10⁻⁴). This variant was also significant after Bonferroni correction.

Conclusions

These results indicate that a genetic variant in OPG is associated with a more severe rate of joint destruction in RA.     

Auxin influx activity is associated with Frankia infection during actinorhizal nodule formation in Casuarina glauca

Plants from the Casuarinaceae family enter symbiosis with the actinomycete Frankia leading to the formation of nitrogen-fixing root nodules. We observed that application of the auxin influx inhibitor 1-naphtoxyacetic acid perturbs actinorhizal nodule formation. This suggests a potential role for auxin influx carriers in the infection process. We therefore isolated and characterized homologs of the auxin influx carrier (AUX1-LAX) genes in Casuarina glauca. Two members of this family were found to share high levels of deduced protein sequence identity with Arabidopsis (Arabidopsis thaliana) AUX-LAX proteins. Complementation of the Arabidopsis aux1 mutant revealed that one of them is functionally equivalent to AUX1 and was named CgAUX1. The spatial and temporal expression pattern of CgAUX1 promoter:beta-glucuronidase reporter was analyzed in Casuarinaceae. We observed that CgAUX1 was expressed in plant cells infected by Frankia throughout the course of actinorhizal nodule formation. Our data suggest that auxin plays an important role during plant cell infection in actinorhizal symbioses.     

Susceptibility to experimental Lyme arthritis correlates with KC and monocyte chemoattractant protein-1 production in joints and requires neutrophil recruitment via CXCR2

The development of experimental Lyme arthritis has been correlated with the expression of a number of chemokines and cytokines, however, none of these have been measured directly from the arthritic joint. We examined the temporal expression of IL-1beta, IL-4, IL-6, IL-10, IL-12p70, GM-CSF, IFN-gamma, TNF-alpha, macrophage inflammatory protein-2, KC, macrophage inflammatory protein-1alpha, and monocyte chemoattractant protein-1 directly from the tibiotarsal joint in arthritis-resistant C57BL/6 (B6) and -susceptible C3H/He (C3H) mice. Only the chemokines KC and monocyte chemoattractant protein-1 were differentially expressed in joints of B6 and C3H mice and correlated with the development of Lyme arthritis. Infection of CXCR2(-/-) mice on either genetic background resulted in a significant decrease in the development of pathology, although infection of CCR2(-/-) mice had little or no effect. Neutrophils in CXCR2(-/-) mice were marginalized within blood vessels and could not enter the joint tissue. These results suggest that chemokine-mediated recruitment of neutrophils into the infected joint is a key requirement for the development of experimental Lyme arthritis.     

Lipopolysaccharide-induced priming of the human neutrophil is not associated with a change in phosphotyrosine phosphatase activity.

The activation of the neutrophil respiratory burst is a two-step process involving an initial 'priming' phase followed by a 'triggering' event. The biochemical mechanisms which underlie these events are yet to be fully elucidated, but the evidence suggests a crucial role for stimulus-induced tyrosine phosphorylation. The enhanced tyrosine phosphorylation observed upon triggering primed cells may reflect an increase in tyrosine kinase activity or a reduction in the levels of the opposing phosphotyrosine phosphatases (PTPases). We have investigated the latter by examining the possibility that lipopolysaccharide (LPS)-induced priming of the neutrophil respiratory burst involves the suppression of cellular PTPase activity. Purified human neutrophils were incubated for 60 min with and without LPS. Priming of the respiratory burst was confirmed by fMet-Leu-Phe-induced cytochrome c reduction. The level of PTPase activity was assessed by dephosphorylation of [32P]RR-src peptide as substrate. Pretreatment of human neutrophils with 200 ng/ml LPS induced a 2.9 +/- 0.3 (mean +/- SEM, n = 3, P = 0.022) fold increase in the fMet-Leu-Phe-triggered respiratory burst. In the same cells, LPS did not induce a significant change in the total cellular PTPase activity (1.02 +/- 0.02-fold, mean +/- SEM, n = 3, P = 0.63). Similarly, stimulation of neutrophils with fMet-Leu-Phe or phorbol myristate acetate did not significantly affect the cellular PTPase activity (P = 0.94 and 0.68, respectively). Our results suggest that suppression of PTPase activity is not the mechanism underlying the priming and/or triggering of the neutrophil respiratory burst.     

A profile of immune response to herpesvirus is associated with radiographic joint damage in rheumatoid arthritis

Introduction  

Progression of joint damage despite appropriate therapy remains a significant problem for patients with rheumatoid arthritis (RA). This study was undertaken to identify profiles of immune response that correlate with radiographic joint damage as a first step toward the discovery of new pathogenic mechanisms of joint destruction in RA.     

Relaxin's induction of metalloproteinases is associated with the loss of collagen and glycosaminoglycans in synovial joint fibrocartilaginous explants

Diseases of specific fibrocartilaginous joints are especially common in women of reproductive age, suggesting that female hormones contribute to their etiopathogenesis. Previously, we showed that relaxin dose-dependently induces matrix metalloproteinase (MMP) expression in isolated joint fibrocartilaginous cells. Here we determined the effects of relaxin with or without β-estradiol on the modulation of MMPs in joint fibrocartilaginous explants, and assessed the contribution of these proteinases to the loss of collagen and glycosaminoglycan (GAG) in this tissue. Fibrocartilaginous discs from temporomandibular joints of female rabbits were cultured in medium alone or in medium containing relaxin (0.1 ng/ml) or β-estradiol (20 ng/ml) or relaxin plus β-estradiol. Additional experiments were done in the presence of the MMP inhibitor GM6001 or its control analog. After 48 hours of culture, the medium was assayed for MMPs and the discs were analyzed for collagen and GAG concentrations. Relaxin and β-estradiol plus relaxin induced the MMPs collagenase-1 and stromelysin-1 in fibrocartilaginous explants – a finding similar to that which we observed in pubic symphysis fibrocartilage, but not in articular cartilage explants. The induction of these proteinases by relaxin or β-estradiol plus relaxin was accompanied by a loss of GAGs and collagen in joint fibrocartilage. None of the hormone treatments altered the synthesis of GAGs, suggesting that the loss of this matrix molecule probably resulted from increased matrix degradation. Indeed, fibrocartilaginous explants cultured in the presence of GM6001 showed an inhibition of relaxin-induced and β-estradiol plus relaxin-induced collagenase and stromelysin activities to control baseline levels that were accompanied by the maintenance of collagen or GAG content at control levels. These findings show for the first time that relaxin has degradative effects on non-reproductive synovial joint fibrocartilaginous tissue and provide evidence for a link between relaxin, MMPs, and matrix degradation.     

Relaxin's induction of metalloproteinases is associated with the loss of collagen and glycosaminoglycans in synovial joint fibrocartilaginous explants

Diseases of specific fibrocartilaginous joints are especially common in women of reproductive age, suggesting that female hormones contribute to their etiopathogenesis. Previously, we showed that relaxin dose-dependently induces matrix metalloproteinase (MMP) expression in isolated joint fibrocartilaginous cells. Here we determined the effects of relaxin with or without beta-estradiol on the modulation of MMPs in joint fibrocartilaginous explants, and assessed the contribution of these proteinases to the loss of collagen and glycosaminoglycan (GAG) in this tissue. Fibrocartilaginous discs from temporomandibular joints of female rabbits were cultured in medium alone or in medium containing relaxin (0.1 ng/ml) or beta-estradiol (20 ng/ml) or relaxin plus beta-estradiol. Additional experiments were done in the presence of the MMP inhibitor GM6001 or its control analog. After 48 hours of culture, the medium was assayed for MMPs and the discs were analyzed for collagen and GAG concentrations. Relaxin and beta-estradiol plus relaxin induced the MMPs collagenase-1 and stromelysin-1 in fibrocartilaginous explants--a finding similar to that which we observed in pubic symphysis fibrocartilage, but not in articular cartilage explants. The induction of these proteinases by relaxin or beta-estradiol plus relaxin was accompanied by a loss of GAGs and collagen in joint fibrocartilage. None of the hormone treatments altered the synthesis of GAGs, suggesting that the loss of this matrix molecule probably resulted from increased matrix degradation. Indeed, fibrocartilaginous explants cultured in the presence of GM6001 showed an inhibition of relaxin-induced and beta-estradiol plus relaxin-induced collagenase and stromelysin activities to control baseline levels that were accompanied by the maintenance of collagen or GAG content at control levels. These findings show for the first time that relaxin has degradative effects on non-reproductive synovial joint fibrocartilaginous tissue and provide evidence for a link between relaxin, MMPs, and matrix degradation.     

The sequential generation of neutrophil chemoattractant proteins in acute inflammation in the rabbit in vivo. Relationship between C5a and proteins with the characteristics of IL-8/neutrophil-activating protein 1

An in vivo experimental peritonitis model was investigated in the rabbit using zymosan as the inflammatory stimulus. After an i.p. injection of zymosan, exudate was removed at intervals and tested in the back skin of assay rabbits. Assay rabbits received i.v. injections of 125I-albumin and 111In-neutrophils, and the local accumulation of each label was measured in response to intradermal injections of exudate samples mixed with a potentiating dose of PGE2. When peritoneal exudate samples were tested in the presence of a specific anti-C5a antibody, virtually all the edema-inducing and neutrophil chemoattractant activity was abolished in samples taken up to 2 h after the zymosan injection. Later samples, however, contained increasing levels of a non-C5a component. In C5a-depleted 6-h exudate two peaks of inflammatory activity were separated using cation exchange HPLC. Evidence is presented that C5a itself is unable to stimulate the production of these activities. Both peaks of activity appear related to IL-8/NAP-1 as they inhibited the binding of 125I-IL-8/NAP-1 to human neutrophils.     

Recent experimental and clinical findings in the skeleton associated with loss of estrogen hormone or estrogen receptor activity

Studies on rodent models and rare human disorders of estrogen production or response have revealed an increased complexity of the actions of estrogen on bone. ERα disruption in human males results in delayed epiphyseal maturation, tall stature, trabecular thinning, marked cortical thinning, genu valgum and significantly reduced cortical vBMD, but trabecular number is preserved and there is normal to increased periosteal expansion. Aromatase deficiency results overall in a similar phenotype, although less is known about skeletal architecture. Importantly, estrogen replacement in these individuals, even if provided late in the third decade, may normalize aBMD. Less certain is whether there is complete recovery of normal skeletal architecture and strength. Rodent models, in general, are consistent with the human phenotype but are confounded by inherent differences between mouse and human physiology and issues regarding the completeness of the different knock-out lines. Both human and rodent studies suggest that residual effects of estrogen through ERβ, truncated ERα forms or nonclassical estrogen receptors might account for different phenotypes in the hERKO man, aromatase deficient subjects and rodents. Importantly, androgen, particularly by preserving trabecular number and augmenting both periosteal and epiphyseal growth, also has significant actions on bone.     

Existing joint erosions increase the risk of joint space narrowing independently of clinical synovitis in patients with early rheumatoid arthritis

IntroductionClinical synovitis is often associated with damage to bone and cartilage. Previous data have suggested that joint erosions (JE) are more prevalent than joint space narrowing (JSN) and that the two processes are partly independent of each other. The objective of this study was to evaluate whether the presence of JE in an individual joint can lead to development of JSN and if existing JSN leads to new onset of JE, in the absence of synovitis.MethodsThe Prospective Multi-Centre Randomised, Double-Blind, Active Comparator-Controlled, Parallel-Groups Study Comparing the Fully Human Monoclonal Anti-TNFα Antibody Adalimumab Given Every Second Week With Methotrexate Given Weekly and the Combination of Adalimumab and Methotrexate Administered Over 2 Years in Patients With Early Rheumatoid Arthritis (PREMIER) enrolled early rheumatoid arthritis (RA) patients who were randomized to one of three treatments: methotrexate (MTX), adalimumab (ADA), or ADA + MTX. All evaluable joints with JE and JSN measures at 26 and 52 weeks and synovitis assessments from week 26 to 52 were included. Synovitis was assessed every 2–8 weeks by swollen joint counts between weeks 26 and 52. Radiographs were taken at week 26 and 52. Two readers, blinded to time and sequence, scored 14 bilateral joints individually for JE and JSN. Multivariate logistic modeling was used to characterize the dependence of JE/JSN onset at 52 weeks. Analyses were performed based on treatment arm and were also performed within individual joints.ResultsJE and swelling were independently and comparably associated with onset of JSN at week 52. Assessment by individual joints indicated that existing JE, independent of swelling, was significantly associated with JSN onset in higher proportions of metatarsophalangeal (MTP; 7/10) than proximal interphalangeal (PIP; 1/8) or metacarpophalangeal (MCP; 1/10) joints. Treatment with ADA + MTX prevents JE/JSN progression independently of its ability to suppress synovitis and limits JE/JSN onset and progression in joints with existing damage.ConclusionsExisting JE predisposes individual joints to development of JSN independently of synovitis in the same joint. Weight-bearing MTP joints with JE may be at increased risk for JSN when compared with MCPs and PIPs.

Trial registration

Clinicaltrials.gov {"type":"clinical-trial","attrs":{"text":"NCT00195663","term_id":"NCT00195663"}}NCT00195663. Registered 13 September 2005.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0626-1) contains supplementary material, which is available to authorized users.     

Interleukin-7-aggravated joint inflammation and tissue destruction in collagen-induced arthritis is associated with T-cell and B-cell activation

Introduction

We sought to investigate the capacity of interleukin (IL)-7 to enhance collagen-induced arthritis and to study by what mechanisms this is achieved.

Methods

Mice received multiple injections with IL-7 or phosphate-buffered saline (PBS) as a control. Arthritis severity and incidence were determined by visual examination of the paws. Joint destruction was determined by assessing radiographs and immunohistochemistry of the ankle joints. Total cellularity and numbers of T-cell and B-cell subsets were assessed, as well as ex vivo production of interferon-γ (IFN-γ), IL-17, and IL-4. Proinflammatory mediators were measured in serum with multianalyte profiling.

Results

IL-7 increased arthritis severity and radiology-assessed joint destruction. This was consistent with IL-7-increased intensity of cell infiltrates, bone erosions, and cartilage damage. Splenic CD19⁺ B cells and CD19⁺/GL7⁺ germinal center B cells, as well as CD4 and CD8 numbers, were increased by IL-7. IL-7 expanded memory T cells, associated with increased percentages of IFN-γ-, IL-4-, and IL-17-producing CD4⁺ T cells. On antigen restimulation of draining lymph node cells in vitro IL-7 treatment was found to increase IFN-γ and IL-17 production, whereas IL-4 was reduced. IL-7 also increased concentrations of proinflammatory mediators, indicative of T-cell activation (sCD40L), vascular activation (VCAM-1, VEGF), tissue destruction (fibroblast growth factor-basic (FGF-b), LIF), and chemotaxis (MIP-1γ, MIP-3β, lymphotactin, MDC, and MCP-5).

Conclusions

In arthritic mice, IL-7 causes expansion of T and B cells, associated with increased levels of proinflammatory mediators. IL-7 intensifies arthritis severity and joint destruction, accompanied by increased Th1 and Th17 activity. These data indicate that IL-7 could be an important mediator in arthritic conditions and that targeting IL-7 or its receptor represent novel therapeutic strategies.     

Drinking water is associated with weight loss in overweight dieting women independent of diet and activity

Background: Data from short‐term experiments suggest that drinking water may promote weight loss by lowering total energy intake and/or altering metabolism. The long‐term effects of drinking water on change in body weight and composition are unknown, however. Objective: This study tested for associations between absolute and relative increases in drinking water and weight loss over 12 months. Methods and Procedures: Secondary analyses were conducted on data from the Stanford A TO Z weight loss intervention on 173 premenopausal overweight women (aged 25–50 years) who reported <1 l/day drinking water at baseline. Diet, physical activity, body weight, percent body fat (dual‐energy X‐ray absorptiometry), and waist circumference were assessed at baseline, 2, 6, and 12 months. At each time point, mean daily intakes of drinking water, noncaloric, unsweetened caloric (e.g., 100% fruit juice, milk) and sweetened caloric beverages, and food energy and nutrients were estimated using three unannounced 24‐h diet recalls. Beverage intake was expressed in absolute (g) and relative terms (% of beverages). Mixed models were used to test for effects of absolute and relative increases in drinking water on changes in weight and body composition, controlling for baseline status, diet group, and changes in other beverage intake, the amount and composition of foods consumed and physical activity. Results: Absolute and relative increases in drinking water were associated with significant loss of body weight and fat over time, independent of covariates. Discussion: The results suggest that drinking water may promote weight loss in overweight dieting women.     

Site-specific mutations in the N-terminal region of human C5a that affect interactions of C5a with the neutrophil C5a receptor.

C5a is an inflammatory mediator that evokes a variety of immune effector functions including chemotaxis, cell activation, spasmogenesis, and immune modulation. It is well established that the effector site in C5a is located in the C-terminal region, although other regions in C5a also contribute to receptor interaction. We have examined the N-terminal region (NTR) of human C5a by replacing selected residues in the NTR with glycine via site-directed mutagenesis. Mutants of rC5a were expressed as fusion proteins, and rC5a was isolated after factor Xa cleavage. The potency of the mutants was evaluated by measuring both neutrophil chemotaxis and degranulation (beta-glucuronidase release). Mutants that contained the single residue substitutions Ile-6-->Gly or Tyr-13-->Gly were reduced in potency to 4-30% compared with wild-type rC5a. Other single-site glycine substitutions at positions Leu-2, Ala-10, Lys-4, Lys-5, Glu-7, Glu-8, and Lys-14 showed little effect on C5a potency. The double mutant, Ile-6-->Gly/Tyr-13-->Gly, was reduced in potency to < 0.2%, which correlated with a correspondingly low binding affinity for neutrophil C5a receptors. Circular dichroism studies revealed a 40% reduction in alpha-helical content for the double mutant, suggesting that the NTR contributes stabilizing interactions that maintain local secondary or tertiary structure of C5a important for receptor interaction. We conclude that the N-terminal region in C5a is involved in receptor binding either through direct interaction with the receptor or by stabilizing a binding site elsewhere in the intact C5a molecule.     

B lymphocytopenia in rheumatoid arthritis is associated with the DRB1 shared epitope and increased acute phase response

The influence of HLA DRB1 alleles on B-cell homeostasis was analyzed in 164 patients with rheumatoid arthritis (RA). The percentages of CD19⁺ B lymphocytes determined in the peripheral circulation of 94 retrospectively recruited RA patients followed a bimodal distribution. Two frequency peaks (B-cell_low patients and B-cell_high patients) were separated by the population median of a B-cell frequency of 8.5% of all lymphocytes. Human leucocyte antigen genotyping revealed that the B-cell_low patients were more frequently positive for the RA-associated HLA DRB1 shared epitope (SE) than were B-cell_high patients. Accordingly, SE-positive patients had lower CD19 percentages in the rank-sum analysis when compared with SE-negative patients, and were markedly B lymphocytopenic when compared with a healthy control group. To confirm the differential frequencies of CD19⁺ B cells, absolute numbers in peripheral blood were determined prospectively in a cohort of 70 RA patients with recent onset disease. SE-positive patients were found to have lower absolute numbers of circulating CD19⁺ B cells. B-cell counts below the mean of the study population were associated with higher acute phase response and with increased levels of rheumatoid factor IgA. No correlation between absolute numbers of circulating B cells and radiographic progression of joint destruction was seen. The influence of immunogenetic parameters on B-cell homeostasis in RA reported here has not been described previously. The clinical relevance of B lymphocytopenia in SE-positive RA will be further investigated in longitudinal studies.