Infliximab treatment shifts the balance between stimulatory and inhibitory Fcγ receptor type II isoforms on neutrophils in patients with rheumatoid arthritis

Fcgr2b and Fcgr3 are the major genetic factors for cartilage antibody-induced arthritis, overriding the effect of Hc encoding complement C5

Like rheumatoid arthritis (RA) in humans, collagen-induced arthritis (CIA) in mice is associated with not only MHC class II genetic polymorphism but also, to some extent, with other loci including genes encoding Fc gamma receptors (FCGRs) and complement C5. In this study, we used a cartilage antibody-induced arthritis (CAIA) model in which arthritis develops within a 12-h timeframe, to determine the relative importance of FCGRs and C5 (Hc). In CAIA, inhibiting or deleting FCGR3 substantially hindered arthritis development, underscoring the crucial role of this receptor. Blocking FCGR3 also reduced the levels of FCGR4, and vice versa. When employing an IgG1 arthritogenic cocktail that exclusively interacts with FCGR2B and FCGR3, joint inflammation was promptly initiated in Fcgr2b-- mice but not in Fcgr3-- mice, suggesting that FCGR3 is sufficient for CAIA development. Regarding complement activation, Fcgr2b++.Hc** mice with C5 mutated were fully resistant to CAIA, whereas Fcgr2b--.Hc** mice developed arthritis rapidly. We conclude that FCGR3 is essential and sufficient for CAIA development, particularly when induced by IgG1 antibodies. The human ortholog of mouse FCGR3, FCGR2A, may be associated with RA pathogenesis. FCGR2B deficiency allows for rapid arthritis progression and overrides the resistance conferred by C5 deficiency.

Aberrant FcγRIIb and FcγRIII expression on monocytes from patients with Behçet's disease

Behçet's disease (BD) patients have abnormal FcγR polymorphisms, the implication of which remains elusive. We examined FcγRIIb expression on neutrophils, monocytes, B cells, natural killer cells, dendritic cells and T cells, and FcγRI and FcγRIII expression on monocytes in BD patients and healthy controls using flow cytometry. We further stimulated monocytes with IgG and (or) lipopolysaccharide (LPS) and measured IL-6 and TNF-α production by enzyme-linked immunosorbent assay. We found that BD monocytes expressed a lower level of FcγRIIb and a higher level of FcγRIII, which were correlated with erythrocyte sedimentation rate and C-reactive protein and were rescued after treatment. Furthermore, LPS- and IgG-stimulated BD monocytes produced higher levels of IL-6 and TNF-α than HC monocytes. In summary, we found that BD monocytes downregulated FcγRIIb expression and upregulated FcγRIII expression, which were correlated with disease activity and potentially contributed to monocyte hyperactivation in BD.

Genetic polymorphisms of high platelet reactivity in Chinese patients with coronary heart disease under clopidogrel therapy

BACKGROUND

The variability in the clinical response to clopidogrel treatment has been attributed to genetic factors, but the specific genes and other risk factors remain unclear.

OBJECTIVE

To investigate the incidence of high on-treatment platelet reactivity in coronary heart disease patients following clopidogrel therapy by analyzing the correlation between genetic polymorphisms and high on-treatment platelet reactivity.

SETTING

This study was conducted in the Chinese People's Liberation Army (PLA) general hospital.

METHOD

578 patients with coronary heart disease undergoing percutaneous transluminal coronary intervention treatment were enrolled. They received dual antiplatelet therapy with aspirin (300 mg) plus clopidogrel (300 mg) over 24 h, or aspirin (100 mg/day) and clopidogrel (75 mg/day) over 3 days. Patients were divided into two groups according to the adenosine diphosphate inhibition rate. The follow-up lasted at least 12 months and adverse endpoint events were recorded.

MAIN OUTCOME MEASURE

The single nucleotide polymorphisms were detected by MassArray genotyping system.

RESULTS

The incidence of HTPR was 15.74% in total, being higher in females than in males (24.29% vs. 13.01%, P < 0.01). Diabetes mellitus, homocysteine and high sensitivity C-reactive protein (hs-CRP) levels were significantly higher in the HTPR group than those in the non-HTPR group (P < 0.05). Polymorphisms of rs1057910 (OR 2.90, P = 0.003), rs2246709 (OR 0.69, P = 0.039), and rs776746 (OR 0.66, P = 0.034) were associated with the incidence of high on-treatment platelet reactivity. Female patients were prone to polymorphisms of rs1057910 (OR 3.24, P = 0.004) and rs776746 (OR 0.57, P = 0.025). Compared to non-high on-treatment platelet reactivity group, no differences in high reactivity group were observed with coexisting single nucleotide polymorphisms (14.6% vs. 14.8%, P > 0.05). The adverse endpoint events were significantly higher in the high on-treatment platelet reactivity group than in the non-treatment reactivity group. The survival analysis showed that high on-treatment platelet reactivity was significantly associated with the risk of the endpoint events (P = 0.0219).

CONCLUSION

Gender (female), diabetes mellitus, high levels of homocysteine and hs-CRP were risk factors for high on-treatment platelet reactivity, and high reactivity was a strong predictor for adverse endpoint events in the coronary heart disease patients. The polymorphism of rs1057910 was a risk factor of high on-treatment platelet reactivity while rs2246709 and rs776746 polymorphisms were protective factors, and coexisting single nucleotide polymorphisms didn't increase the incidence of high on-treatment platelet reactivity.

Rheumatoid arthritis and systemic lupus erythematosus: Pathophysiological mechanisms related to innate immune system

Rheumatoid arthritis and systemic lupus erythematosus are two highly prevalent autoimmune diseases that generate disability and low quality of life. The innate immune system, a long-forgotten issue in autoimmune diseases, is becoming increasingly important and represents a new focus for the treatment of these entities. This review highlights the role that innate immune system plays in the pathophysiology of rheumatoid arthritis and systemic lupus erythematosus. The role of the innate immune system in rheumatoid arthritis and systemic lupus erythematosus pathophysiology is not only important in early stages but is essential to maintain the immune response and to allow disease progression. In rheumatoid arthritis, genetic and environmental factors are involved in the initial stimulation of the innate immune response in which macrophages are the main participants, as well as fibroblast-like synoviocytes. In systemic lupus erythematosus, all the cells contribute to the inflammatory response, but the complement system is the major effector of the inflammatory process. Detecting alterations in the normal function of these cells, besides its contribution to the understanding of the pathophysiology of autoimmune diseases, could help to establish new treatment strategies for these diseases.

Increased exercise-related platelet activation assessed by impedance aggregometry in diabetic patients despite aspirin therapy

Aspirin is widely used for the prevention of thromboembolic diseases, but inhibition of platelet aggregation (PA) is not uniform. Additionally, aspirin has been shown to be ineffective in blunting PA in response to exercise in patients with coronary artery disease (CAD). Limited data exists about platelet function following acute exercise in diabetics taking aspirin. In our study, we aimed to investigate PA before and after exercise stress test in type-2 diabetic patients taking aspirin. Forty-three patients with type-2 diabetes mellitus (DM) and 36 subjects (age- and sex-matched) as control group were included prospectively. All participants were under aspirin (100 mg/day) therapy for at least 1 week. The measures of PA were assessed by impedance aggregometry using arachidonic acid as an agonist (ASPI test). Blood samplings were undertaken before and immediately after treadmill exercise test. At rest, diabetic and control groups had comparable pre-exercise PA (22.97 ± 14.57 versus 22.11 ± 12.71 AU min, p = NS, respectively). After treadmill exercise, both groups showed significantly higher absolute increase (9.02 ± 13.08 and 3.66 ± 5.87 AU min, p < 0.01, p < 0.01, respectively) and percent (%) increase (45.67 ± 49.34 and 24.04 ± 46.59 AU min, p < 0.01, p = 0.01, respectively) in PA. Both absolute increase (p < 0.05) and % increase (p < 0.05) in PA were significantly higher in DM group compared to the control group. Multiple regression analysis revealed that high-sensitive C-reactive protein (p = 0.014) was independent predictor of absolute increase PA. Our study showed that aspirin has limited effect in inhibiting exercise-induced PA, even in the absence of documented CAD. The increase in PA following exercise was significantly greater in patients with DM compared with controls.

Aspirin in primary prevention for patients with diabetes: Still a matter of debate

BACKGROUND

Patients with diabetes are at high cardiovascular (CV) risk due to an exaggerated platelet activation and aggregation. In the first 2000s low-dose aspirin was first recommended for primary prevention, but then re-discussed.

METHODS

This short narrative review, based on the material searched for and obtained via PubMed up to February 2018, aims at clarifying this controversial topic.

RESULTS

The JPAD2 study has been designed to evaluate the occurrence of any CV event in a cohort of patients with diabetes and concluded that low-dose aspirin did not influence the risk for CV events while increasing the risk for gastrointestinal (GI) bleeding. Reasons for this result can be found in the role of diabetic platelets, which are known to be hyperreactive, thus producing intensified adhesion, activation, and aggregation. In this setting, other associated metabolic conditions can concur to enhance platelet adhesion and activation. Aspirin resistance has been often considered a guilty actor, although many mechanisms have been mistaken for true aspirin resistance, such as patient poor compliance, inadequate dosing, drug interactions, and high-platelet turnover. However, the mere presence of diabetes is not likely to give a net benefit for CV protection with respect to GI bleeding.

CONCLUSION

It appears advisable to follow current guidelines addressing first of all classical risk factors and evaluate aspirin therapy in primary prevention only for patients with type 1 or 2 diabetes at increased CV risk and no risk for GI bleeding. Anyway, additional clinical trials are needed to address the current topic.

Diabetes and antiplatelet therapy: from bench to bedside

Diabetes mellitus (DM) is a metabolic disorder associated with accelerated atherogenesis and an increased risk of atherothrombotic complications. Multiple mechanisms contribute to the pro-thrombotic status which characterizes DM patients underscoring the importance of antiplatelet therapies used for secondary prevention in these patients. For many years, dual antiplatelet therapy (DAPT) with aspirin and the P2Y₁₂ inhibitor clopidogrel has represented the mainstay of treatment following an acute coronary syndrome (ACS) or in patients undergoing percutaneous coronary interventions (PCI). Although DAPT reduces the incidence of atherothrombotic recurrences, these rates remain high in DM patients underscoring the need for more efficacious therapies. Oral platelet P2Y₁₂ receptor inhibitors with enhanced potency, such as prasugrel and ticagrelor, as well as antiplatelet therapies such as vorapaxar inhibiting the thrombin-mediated platelet signaling pathway, constitute treatment opportunities for patients with DM and have shown to be associated with a greater reduction in ischemic recurrences, albeit at the cost of more bleeding. This article reviews currently available antiplatelet agents and delivers an update on the advances and drawbacks of these agents used for secondary prevention in DM patients experiencing an ACS or undergoing PCI.

Endothelial dysfunction and platelet hyperactivity in type 2 diabetes mellitus: molecular insights and therapeutic strategies

The incidence and prevalence of diabetes mellitus is rapidly increasing worldwide at an alarming rate. Type 2 diabetes mellitus (T2DM) is the most prevalent form of diabetes, accounting for approximately 90-95% of the total diabetes cases worldwide. Besides affecting the ability of body to use glucose, it is associated with micro-vascular and macro-vascular complications. Augmented atherosclerosis is documented to be the key factor leading to vascular complications in T2DM patients. The metabolic milieu of T2DM, including insulin resistance, hyperglycemia and release of excess free fatty acids, along with other metabolic abnormalities affects vascular wall by a series of events including endothelial dysfunction, platelet hyperactivity, oxidative stress and low-grade inflammation. Activation of these events further enhances vasoconstriction and promotes thrombus formation, ultimately resulting in the development of atherosclerosis. All these evidences are supported by the clinical trials reporting the importance of endothelial dysfunction and platelet hyperactivity in the pathogenesis of atherosclerotic vascular complications. In this review, an attempt has been made to comprehensively compile updated information available in context of endothelial and platelet dysfunction in T2DM.

Activation status of peripheral blood neutrophils and the complement system in adult rheumatoid arthritis patients undergoing combined therapy with infliximab and methotrexate

We examined the functional activity of peripheral blood neutrophils and the complement system activation status in patients with rheumatoid arthritis (RA) undergoing infliximab/methotrexate combined therapy. We studied female RA patients under treatment with infliximab (3-5 mg/kg) and methotrexate (15-25 mg/week) who presented inactive (i-RA; n = 34, DAS-28 ≤ 2.6) or at least moderately active disease (a-RA; n = 29, DAS-28 > 3.2), and age-matched healthy women (n = 38). We measured the levels of reactive oxygen species (ROS) generation (chemiluminescence assay) and membrane expression of FcγRIIa/CD32, FcγRIIIb/CD16, CR1/CD35, and CR3/CD11b receptors (ELISA assay) in neutrophils. We also determined the hemolytic activity of the alternative and classical pathways of the complement system (spectrophotometry), serum levels of C5a and Bb (ELISA assay), and serum chemotactic activity (Boyden chamber). Compared with the control group, i-RA and a-RA patients exhibited: (1) increased neutrophil ROS production and membrane expression of FcγRIIa/CD32, FcγRIIIb/CD16, and CR1/CD35, indicating neutrophil activation; and (2) increased serum chemotactic activity and decreased activity of the alternative complement pathway, indicating systemic complement system activation. The levels of C-reactive protein in a-RA patients were augmented, compared with i-RA patients. Although infliximab/methotrexate combined therapy induced disease remission according to the DAS-28 criteria, both i-RA and a-RA patients still exhibited significant levels of systemic activation of neutrophils and the complement system.

Circulating T cells to infliximab are detectable mainly in treated patients developing anti-drug antibodies and hypersensitivity reactions

Antibodies recognizing infliximab (IFX) may develop in a proportion of treated patients, leading to loss of response or hypersensitivity reactions (HRs). T cell response to IFX has been poorly investigated. This paper was addressed to detect IFX‐specific T cells in treated patients with inflammatory diseases developing, or not, anti‐drug antibodies (ADA) and to correlate the presence of specific T cells with the clinical outcomes of the treatment. A co‐culture system of IFX‐loaded dendritic cells and purified autologous CD4⁺ T cells was used to detect memory T cells in 32 ADA⁺ and 39 ADA^– IFX‐treated patients and control groups. The cytokine profile of IFX‐specific T cells was also studied in culture supernatants. IFX‐specific cell proliferation was detected mainly in cells from ADA⁺ patients, irrespective of their different diseases. HR patients displayed higher T cell proliferation than non‐responder and tolerant patients. A mixed [interferon (IFN)‐γ, interleukin (IL)‐13, IL‐10] cytokine profile was shown in cells from ADA⁺ patients, while IL‐10 was the most frequently detected cytokine in the supernatants of cultures from ADA‐ patients. Immunoglobulin (Ig)E⁺ADA⁺ patients with previous HRs exhibited a more pronounced type 2 profile than IgE^–ADA⁺ patients. This work provides evidence that IFX‐specific circulating T cells are detectable mainly in ADA⁺ patients with HRs, regardless of their disease. The IFX‐induced cytokine pattern partially correlates with the ADA isotype.

Thrombopoietin receptor agonists shift the balance of Fcγ receptors toward inhibitory receptor IIb on monocytes in ITP

Elevated expression of the activating Fcγ receptor (FcγR) I and FcγRIIa together with decreased expression of the inhibitory FcγRIIb are involved in the pathogenesis of primary immune thrombocytopenia (ITP). Thrombopoietin receptor agonists (TPO-RAs) have been used clinically for the management of ITP; however, little is known about the effect of TPO-RAs on FcγR modulation in ITP. In this prospective study, we measured the alteration in monocyte FcγR expression from 21 corticosteroid-resistant/relapsed patients with chronic ITP receiving eltrombopag therapy. Results showed that the mRNA and protein levels of FcγRIIb were significantly elevated after 6-week eltrombopag treatment. Concurrently, FcγRI and IIa levels decreased remarkably, whereas FcγRIII expression did not change. In vitro phagocytosis assays indicated that a shift in the balance of FcγR toward inhibitory FcγRIIb on monocytes was accompanied with a considerable decrease in monocyte/macrophage phagocytic capacity. The response to eltrombopag therapy in patients with ITP was associated with FcγR phenotype and functional changes of monocytes/macrophages. Moreover, the plasma transforming growth factor-β1 (TGF-β1) concentrations increased significantly in eltrombopag responders. Modulation of monocyte FcγR balance by TPO-RAs was also found in a murine model of ITP established by transferring splenocytes from immunized CD61 knockout mice into CD61(+) severe combined immunodeficient mice. Romiplostim administration in ITP mice significantly upregulated inhibitory FcγRII expression and downregulated activating FcγRI expression. These findings showed that recovery of platelet counts after TPO-RA treatment in ITP is associated with the restoration of FcγR balance toward the inhibitory FcγRIIb on monocytes, and suggested that thrombopoietic agents have a profound effect on immune modulation in ITP. This study is registered at ClinicalTrials.gov as #NCT01864512.

FcγR requirements leading to successful immunotherapy

Monoclonal antibody (mAb) immunotherapy is currently experiencing an unprecedented amount of success, delivering blockbuster sales for the pharmaceutical industry. Having experienced several false dawns and overcoming technical issues which limited progress, we are now entering a golden period where mAbs are becoming a mainstay of treatment regimes for diseases ranging from cancer to autoimmunity. In this review, we discuss how these mAbs are most likely working and focus in particular on the key receptors that they interact with to precipitate their therapeutic effects. Although their targets may vary, their engagement with Fcγ receptors (FcγRs) on numerous immune effector cells is almost universal, and here we review their roles in delivering successful immunotherapy.

Targeting the Fc receptor in autoimmune disease

INTRODUCTION

The Fc receptors (FcRs) and their interactions with immunoglobulin and innate immune opsonins, such as C-reactive protein, are key players in humoral and cellular immune responses. As the effector mechanism for some therapeutic monoclonal antibodies, and often a contributor to the pathogenesis and progression of autoimmunity, FcRs are promising targets for treating autoimmune diseases.

AREAS COVERED

This review discusses the nature of different FcRs and the various mechanisms of their involvement in initiating and modulating immunocyte functions and their biological consequences. It describes a range of current strategies in targeting FcRs and manipulating their interaction with specific ligands, while presenting the pros and cons of these approaches. This review also discusses potential new strategies including regulation of FcR expression and receptor crosstalk.

EXPERT OPINION

FcRs are appealing targets in the treatment of inflammatory autoimmune diseases. However, there are still knowledge limitations and technical challenges, the most important being a better understanding of the individual roles of each of the FcRs and enhancement of the specificity in targeting particular cell types and specific FcRs.

High-dose methylprednisolone pulse therapy upregulated FcγRIIb expression on B cells in primary Sjögren's syndrome patients with thrombocytopenia

Abnormalities in B cell are characteristic feature of primary Sjögren's syndrome (pSS). As FcγRIIb is a key regulator of B cells, the objective of this study is to investigate the role of the inhibitory receptor FcγRIIb in B cells from pSS patients, and whether glucocorticoid can affect B cell subpopulations or FcγRIIb expression. Thirty pSS patients and 15 healthy controls were enrolled in this study. The results showed that the percentage of memory CD19(+)CD27(+) B cells was significantly lower in pSS patients compared to in healthy controls. FcγRIIb expression on memory CD19(+)CD27(+) B cells from active pSS patients was significantly reduced compared with those from inactive or healthy controls. The level of FcγRIIb on memory CD19(+)CD27(+) B cells from active pSS patients was negatively correlated with anti-SSA antibody titers and Sjögren's syndrome disease activity index. After a high-dose methylprednisolone pulse therapy for 3 days, FcγRIIb expression on memory B cells was upregulated, with the raised level of platelets. In vitro, dexamethasone could elevate FcγRIIb expression on B cells of pSS patients in a dose-dependent manner. Taken together, our data suggest that the upregulation of FcγRIIb may be expected to be a new therapeutic strategy in pSS patients.

Cross-linking of IgGs bound on circulating neutrophils leads to an activation of endothelial cells: possible role of rheumatoid factors in rheumatoid arthritis-associated vascular dysfunction

BACKGROUND

Rheumatoid arthritis is characterized by the presence of circulating auto-antibodies, including rheumatoid factors, which recognize the Fc portion of IgGs. The neutrophil is the most abundant circulating leukocyte and it expresses high levels of FcγRs on its surface. The aim of the present study was to examine the capacity of circulating human neutrophils to be activated by rheumatoid factors and the consequences of these events on endothelium.

METHODS

Neutrophil-bound IgGs were cross-linked with anti-human IgGs to mimick the presence of circulating rheumatoid factors and FcγRs-dependent signalling events and functions were examined. The IgG and IgM composition of rheumatoid factors isolated from the serum of RA patients was characterized. Adhesion of neutrophils to endothelial cells was quantified in response to the addition of rheumatoid factors.

RESULTS

Cross-linking of IgGs bound on neutrophils leads to FcγRs-dependent tyrosine phosphorylation, mobilisation of intracellular calcium and the extracellular release of superoxide anions and lysozyme. Incubation of endothelial cells with the supernatant of activated neutrophils increases ICAM-1 expression and IL-8 production by endothelial cells. Finally, rheumatoid factors enhance neutrophil adhesion to endothelial cells.

CONCLUSIONS

Our results show that activation of neutrophils' FcγRs by rheumatoid factors could participate in rheumatoid arthritis-associated vascular damage.

Platelet function in patients with diabetes mellitus: from a theoretical to a practical perspective

Patients with diabetes mellitus have an increased prevalence of vascular disease. Pathologic thrombosis associated with atherosclerotic plaque rupture is a major cause of morbidity and mortality. Platelets are intimately involved in the initiation and propagation of thrombosis. Evidence suggests that platelets from patients with type 2 diabetes have increased reactivity and baseline activation compared to healthy controls. We review the pathophysiology of platelet hyperreactivity in DM patients and its implications in clinical practice, with particular focus on acute coronary syndromes, percutaneous coronary intervention, and novel antiplatelet agents.

High-dose dexamethasone shifts the balance of stimulatory and inhibitory Fcgamma receptors on monocytes in patients with primary immune thrombocytopenia

The human Fcγ receptor (FcγR) system is composed of 2 opposing families, the activating FcγRs (FcγRI, FcγRIIa, and FcγRIII) and the inhibitory FcγR (FcγRIIb). The disturbed balance of the activating and inhibitory FcγRs has been implicated in the pathogenesis of many autoimmune diseases. In this study, the expression of FcγRs on monocytes was determined in 23 patients with primary immune thrombocytopenia (ITP) before and after high-dose dexamethasone (HD-DXM) treatment. The FcγRI expression was significantly higher in ITP patients and decreased after HD-DXM treatment. The ratio of FcγRIIa/IIb mRNA expression on monocytes was significantly higher in untreated patients than in healthy controls. After HD-DXM therapy, the ratio decreased and the increased expression of FcγRIIb mRNA and protein coincided with a remarkable decrease in the expression of FcγRIIa, FcγRI, and monocyte phagocytic capacity. There was no significant difference in FcγRIII expression on monocytes between patients and controls. In vitro cell-culture experiments showed that DXM could induce FcγRIIa and FcγRIIb expression in monocytes from ITP patients, with FcγRIIb at higher amplitudes. These findings suggested that the disturbed FcγR balance might play a role in the pathogenesis of ITP, and that HD-DXM therapy could shift monocyte FcγR balance toward the inhibitory FcγRIIb in patients with ITP.

Platelet abnormalities in diabetes mellitus

Patients with diabetes mellitus (DM) have accelerated atherosclerosis, which is the main underlying factor contributing to the high risk of atherothrombotic events in these patients. Atherothrombotic complications are the leading cause of morbidity and mortality in patients with DM. Among factors contributing to the prothrombotic condition which characterise patients with DM, platelet hyperreactivity plays a pivotal role. Platelets of DM patients are characterised by dysregulation of several signalling pathways leading to intensified adhesion, activation and aggregation. Multiple mechanisms are involved in platelet dysfunction of patients with DM, which can be categorised as follows: a) hyperglycaemia, b) insulin deficiency and resistance, c) associated metabolic conditions, and d) other cellular abnormalities.The present manuscript aims to provide an overview on the current status of knowledge on platelet abnormalities that characterise patients with DM.

FcgammaRIIB in autoimmunity and infection: evolutionary and therapeutic implications

FcgammaRIIB is the only inhibitory Fc receptor. It controls many aspects of immune and inflammatory responses, and variation in the gene encoding this protein has long been associated with susceptibility to autoimmune disease, particularly systemic lupus erythematosus (SLE). FcgammaRIIB is also involved in the complex regulation of defence against infection. A loss-of-function polymorphism in FcgammaRIIB protects against severe malaria, the investigation of which is beginning to clarify the evolutionary pressures that drive ethnic variation in autoimmunity. Our increased understanding of the function of FcgammaRIIB also has potentially far-reaching therapeutic implications, being involved in the mechanism of action of intravenous immunoglobulin, controlling the efficacy of monoclonal antibody therapy and providing a direct therapeutic target.

B cells from rheumatoid arthritis patients show important alterations in the expression of CD86 and FcgammaRIIb, which are modulated by anti-tumor necrosis factor therapy

Introduction

Several molecules help preserve peripheral B cell tolerance, but when altered, they may predispose to autoimmunity. This work studied the expression of the costimulatory molecule CD86 and the inhibitory receptor for IgG immune complexes FcγRIIb (CD32b), on B cells from rheumatoid arthritis (RA) patients, and the influence of anti-tumor necrosis factor (TNF) therapy.

Methods

Peripheral B cells from 18 RA patients and 13 healthy donors were characterized using flow cytometry. Eleven patients who underwent a six-month adalimumab therapy were further assessed for phenotypic changes on their B cells.

Results

RA patients exhibited a high percentage of naïve and memory B cells expressing CD86. In contrast, expression of FcγRIIb was significantly reduced on RA memory B cells and plasmablasts as compared to healthy donors, probably due to downregulation of this receptor when differentiating from naïve to memory cells. These alterations on FcγRIIb were associated with high levels of anti-citrullinated vimentin autoantibodies. In addition, treatment with adalimumab normalized the expression of CD86 on memory B cells and reduced the expression of FcγRIIb, mainly on naïve B cells.

Conclusions

Our findings show that peripheral B cells from RA patients have an altered expression of key molecules, such as CD86 and FcγRIIb. Because this latter receptor is required for feedback inhibition, a deficient expression might contribute to humoral autoimmune responses. Furthermore, these molecules are likely to be influenced by inflammatory factors, since they were modulated by TNF inhibition.

Neutrophil function in inflammation and inflammatory diseases

In inflammatory conditions such as RA, the neutrophil has tended to be dismissed as a short-lived, terminally differentiated, irrelevant bystander cell. However, this is clearly not the case. A better understanding of the complex heterogeneous pathways and processes that constitute RA, in parallel with a more sophisticated knowledge of neutrophil biology has identified many potential roles for these cells in the persistence of inflammation and progression of joint damage, which should not be underestimated. Not only are neutrophils found in high numbers within the rheumatoid joint, both in synovial tissue and in joint fluid, they have a huge potential to directly inflict damage to tissue, bone and cartilage via the secretion of proteases and toxic oxygen metabolites, as well as driving inflammation through antigen presentation and secretion of cytokines, chemokines, prostaglandins and leucotrienes. Drugs already used to treat RA down-regulate many neutrophil functions, including migration to the joint, degranulation and production of inflammatory mediators, and these cells should be considered as important targets for the development of new therapies in the future.

Fcgamma-receptor IIa polymorphism and the role of immunoadsorption in cardiac dysfunction in patients with dilated cardiomyopathy

In patients with dilated cardiomyopathy (DCM), cardiac autoantibodies are able to bind with their Fab fragment to epitopes on cardiomyocytes, but thereafter they crosslink through their Fc fragment to cardiac Fc(gamma)-receptor IIa. Polymorphic variability of the Fc(gamma)-receptor IIa is associated with modified affinity of immunoglobin G (IgG) binding and may influence therapeutic effects. In this study, 103 consecutive DCM patients were treated with immunoadsorption (IA) therapy with subsequent IgG substitution (IA/IgG). Echocardiography was performed at baseline and again at 3 and 6 months after IA/IgG. Fc(gamma)-receptor IIa polymorphism R/H131 was genotyped using a nested sequence-specific primer polymerase chain reaction (PCR). Patients with the Fc(gamma)-receptor IIa genotype R/R131 showed significantly greater improvement in left ventricular (LV) function than patients with the R/H131 or H/H131 genotypes did. Irrespective of the Fc(gamma)-receptor polymorphism, patients with shorter disease duration and a more impaired LV function responded with a greater increase in LV ejection fraction (LVEF). Therefore, the Fc(gamma)-receptor polymorphism influences the efficacy of immunomodulatory therapy involving IA/IgG.

Cross-regulation of signaling by ITAM-associated receptors

An important function of receptors that signal through immunoreceptor tyrosine-based activation motifs (ITAMs) is to regulate signaling by heterologous receptors. This review describes mechanisms by which ITAM-associated receptors modulate signaling by Toll-like receptors (TLRs), tumor necrosis factor receptor family members and cytokine receptors that use the Jak-STAT signaling pathway, and the biological importance of this signal transduction cross-talk. ITAM-mediated cross-regulation can either augment or dampen signaling by other receptors. Conversely, TLRs and cytokines modulate ITAM-mediated signaling, by means including activation of beta2 integrins that are coupled to the ITAM-containing adaptors DAP12 and FcRgamma. Integration of ITAM signaling into signaling networks through cross-talk with other signal transduction pathways results in tight regulation and fine tuning of cellular responses to various extracellular stimuli and contributes to induction of specific activation and differentiation pathways.