Immunoglobulin Free Light Chains in the Pathogenesis of Lung Disorders

Inflammation is an important component of numerous cancers and chronic diseases and many inflammatory mediators have been shown to have potential prognostic roles. Tumor-infiltrating mast cells can promote tumor growth and angiogenesis, but the mechanism of mast cell activation is unclear. Early studies have shown that immunoglobulin free light chains (FLC) can trigger mast cell activation in an antigen-specific manner. Increased expression of FLC is observed within the stroma of many human cancers including those of breast, colon, lung, pancreas, kidney, and skin. These overexpressed FLCs are co-localized to areas of mast cell infiltration. Importantly, FLC expression is associated with basal-like cancers with an aggressive phenotype. Moreover, FLC is expressed in areas of inflammatory cell infiltration and its expression is significantly associated with poor clinical outcome. In addition, serum and bronchoalveolar fluid FLC concentrations are increased in patients with idiopathic pulmonary fibrosis (IPF) and hypersensitivity pneumonitis (HP) compared to control subjects. In this review, we provide an update on the role of FLC in the pathogenesis of several lung disorders and indicate how this may contribute to new therapeutic opportunities.

Mast Cell Degranulation Is Accompanied by the Release of a Selective Subset of Extracellular Vesicles That Contain Mast Cell-Specific Proteases

Mast cells (MC) are well known for their effector role in allergic disorders; moreover, they are associated with diverse modulatory effects in innate and adaptive immunity. It is largely unclear how MC exert these modulating functions. In this article, we show that IgE-mediated MC degranulation leads to a rapid release of high quantities of extracellular vesicles (EV), comparable to the release of preformed mediators. EV are submicron structures composed of lipid bilayers, proteins, and nucleic acids that are released by cells in a regulated fashion and are involved in intercellular communication. Primary murine mucosal-type MC and connective tissue-type MC released phenotypically different EV populations depending on the stimulus they received. Although unstimulated MC constitutively released CD9⁺ EV, degranulation was accompanied by the release of CD63⁺ EV, which correlated with release of the soluble mediator β-hexosaminidase. This CD63⁺ EV subset was smaller and exhibited a higher buoyant density and distinct phospholipid composition compared with CD9⁺ EV. Marked differences were observed for phosphatidylinositol, phosphatidic acid, and bis(monoacylglycero)phosphate species. Strikingly, proteomic analysis of CD63⁺ EV from connective tissue-type MC unveiled an abundance of MC-specific proteases. With regard to carboxypeptidase A3, it was confirmed that the enzyme was EV associated and biologically active. Our data demonstrate that, depending on their activation status, MC release distinct EV subsets that differ in composition and protease activity and are indicative of differential immunological functions. Concerning the strategic tissue distribution of MC and the presence of degranulated MC in various (allergic) disorders, MC-derived EV should be considered potentially important immune regulators.

Comprehensive Proteomic Analysis of Human Milk-derived Extracellular Vesicles Unveils a Novel Functional Proteome Distinct from Other Milk Components

Breast milk contains several macromolecular components with distinctive functions, whereby milk fat globules and casein micelles mainly provide nutrition to the newborn, and whey contains molecules that can stimulate the newborn's developing immune system and gastrointestinal tract. Although extracellular vesicles (EV) have been identified in breast milk, their physiological function and composition has not been addressed in detail. EV are submicron sized vehicles released by cells for intercellular communication via selectively incorporated lipids, nucleic acids, and proteins. Because of the difficulty in separating EV from other milk components, an in-depth analysis of the proteome of human milk-derived EV is lacking. In this study, an extensive LC-MS/MS proteomic analysis was performed of EV that had been purified from breast milk of seven individual donors using a recently established, optimized density-gradient-based EV isolation protocol. A total of 1963 proteins were identified in milk-derived EV, including EV-associated proteins like CD9, Annexin A5, and Flotillin-1, with a remarkable overlap between the different donors. Interestingly, 198 of the identified proteins are not present in the human EV database Vesiclepedia, indicating that milk-derived EV harbor proteins not yet identified in EV of different origin. Similarly, the proteome of milk-derived EV was compared with that of other milk components. For this, data from 38 published milk proteomic studies were combined in order to construct the total milk proteome, which consists of 2698 unique proteins. Remarkably, 633 proteins identified in milk-derived EV have not yet been identified in human milk to date. Interestingly, these novel proteins include proteins involved in regulation of cell growth and controlling inflammatory signaling pathways, suggesting that milk-derived EVs could support the newborn's developing gastrointestinal tract and immune system. Overall, this study provides an expansion of the whole milk proteome and illustrates that milk-derived EV are macromolecular components with a unique functional proteome.

Cigarette smoke differentially modulates dendritic cell maturation and function in time

Background

Dendritic cells (DCs) as professional antigen presenting cells (APCs) play a critical role in the regulation of host immune responses. DCs evolve from immature, antigen-capturing cells, to mature antigen-presenting cells. The relative contribution of DCs to cigarette smoke-induced inflammation is not well documented. In the current study, we investigated a modulatory effect of cigarette smoke extract (CSE) on differentiation, maturation and function of DCs.

Methods

Primary murine DCs were grown from bone marrow cells with GM-CSF. Development of DC was analyzed by expression of CD11c, MHCII, CD86, CD40 and CD83 using flow cytometry. Murine DC’s and human L428 cells were co-cultured with CSE for various periods of time. Functional activity was analyzed by measuring FITC-dextran uptake, cytokine production and the ability to stimulate T cell activation in a mixed lymphocyte reaction.

Results

Our results show that short-term CSE stimulation (~24 h) influence the maturation status of newly differentiated and immature DCs towards more mature cells as revealed by upregulation of MHCII, CD83, CD86, CD40, reduction in antigen up-take capacity and enhanced secretion of pro-inflammatory (IL-12, IL-6 and TNF-α) cytokines. Interestingly, long-term CSE exposure, time- and concentration-dependently, suppressed the development of functional DCs. This suppression was demonstrated by a decline in CD11c/MHCII, CD83, CD86 and CD40 expression, the production of cytokines and ability to stimulate T lymphocytes. Moreover, CSE significantly suppressed the endocytosis function of mouse DCs which was not due to diminished DC viability. Similar to mouse DCs, long-term co-culturing of the human L428 DC cell line with CSE time-dependently suppressed the expression of CD54.

Conclusions

The present study provides evidence that CSE modulates DC-mediated immune responses via affecting both the function and maturation of DCs. The suppressive effects of cigarette smoke on DC function might lead to impaired immune responses to various infections.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-015-0291-6) contains supplementary material, which is available to authorized users.

Dendritic cells inversely regulate airway inflammation in cigarette smoke-exposed mice

The recruitment and activation of inflammatory cells into the respiratory system is considered a crucial feature in the pathophysiology of chronic obstructive pulmonary disease (COPD). Because dendritic cells (DCs) have a pivotal role in the onset and regulation of immune responses, we investigated the effect of modulating DC subsets on airway inflammation by acute cigarette smoke (CS) exposure. CS-exposed mice (5 days) were treated with fms-like tyrosine kinase 3 ligand (Flt3L) and 120g8 antibody to increase total DC numbers and deplete plasmacytoid DCs (pDCs), respectively. Flt3L treatment decreased the number of inflammatory cells in the bronchoalveolar lavage (BALF) of the smoke-exposed mice and increased these in lung tissue. DC modulation reduced IL-17 and increased IL-10 levels, which may be responsible for the suppression of the BALF cells. Furthermore, depletion of pDCs led to increased infiltration of alveolar macrophages while restricting the presence of CD103(+) DCs. This study suggests that DC subsets may differentially and compartment-dependent influence the inflammation induced by CS. pDC may play a role in preventing the pathogenesis of CS by inhibiting the alveolar macrophage migration to lung and increasing CD103(+) DCs at inflammatory sites to avoid extensive lung tissue damage.

The matrikine PGP as a potential biomarker in COPD

The lack of a well-characterized biomarker for the diagnosis of chronic obstructive pulmonary disease (COPD) has increased interest toward finding one, because this would provide potential insight into disease pathogenesis and progression. Since persistent neutrophilia is an important hallmark in COPD Pro-Gly-Pro (PGP), an extracellular matrix-derived neutrophil chemoattractant, has been suggested to be a potential biomarker in COPD. The purpose of this review is to critically examine both biological and clinical data related to the role of PGP in COPD, with particular focus on its role as a clinical biomarker and potential therapeutic target in disease. The data provided in this review will offer insight into the potential use of PGP as end point for future clinical studies in COPD lung disease. Following PGP levels during disease might serve as a guide for the progression of lung disorders.

Association of serum TNF-α, IL-8 and free light chain with HLA-DR B alleles expression in pulmonary and extra-pulmonary sarcoidosis

Background

Sarcoidosis is a systemic disease of unknown etiology characterized histologically by the observation of non-caseating granulomas and several immunological abnormalities. Sarcoidosis is a multi-organ disorder which involves formation of granulomas in many tissues including the lungs (pulmonary) and others such as skin, bone, heart (extra pulmonary). Associations between human leukocyte antigens (HLA), the encoded cell surface receptor (HLA-DR) and sarcoidosis have been reported in several studies. Several HLA-DR alleles have been described as potential risk factors for sarcoidosis in distinct ethnic groups however evidence for a relationship between HLA-DR alleles and pulmonary and extra-pulmonary sarcoidosis (EPS) is still scarce. Although the etiology of the disease remains unclear, infectious and environmental factors have been postulated. Inflammatory cytokines and chemokines may play important roles in the pathogenesis of sarcoidosis and serum free light chain (FLC) numbers have been implicated in several immunologic disorders.

Purpose of the study

The aim of the present study was to investigate HLA associations with serum cytokines and FLC in Iranian patients with pulmonary (n = 86) and EPS (n = 46).

Results

We found that among the 16 HLA DRB alleles only *7 and *12 were different in sarcoidosis patients. The levels of TNF-α and IL-8 in pulmonary sarcoidosis patients were higher than in EPS (P < 0.05) whereas the levels of FLC subunits in EPS were higher than in pulmonary sarcoidosis.

Conclusion

This data may suggests a link between HLA-DRB *12 and sarcoidosis in Iranian population.

Flow cytometry applications in the study of immunological lung disorders

The use of flow cytometry in the clinical laboratory has grown substantially in the past decade. Flow cytometric analysis provides a rapid qualitative and quantitative description of multiple characteristics of individual cells. For example, it is possible to detect the cell size and granularity, aspects of DNA and RNA content and the presence of cell surface and nuclear markers which are used to characterize the phenotype of single cells. Flow cytometry has been used for the immunophenotyping of a variety of specimens including whole blood, bone marrow, serous cavity fluids, (cerebrospinal fluid) CSF, urine and all types of body fluids. The technique has also been applied to human bronchoalveolar lavage (BAL) fluid, peritoneal fluids and blood. In this review, we describe the current status of the application of flow cytometry as a diagnostic tool in various lung diseases. We focus on the analysis of BAL cell composition in chronic obstructive lung disease (COPD), asthma, lung cancer, sarcoidosis, tuberculosis and idiopathic eosinophilic pneumonia (IEP).

Immunoglobulin free light chains are biomarkers of poor prognosis in basal-like breast cancer and are potential targets in tumor-associated inflammation

Inflammation is an important component of various cancers and its inflammatory cells and mediators have been shown to have prognostic potential. Tumor-infiltrating mast cells can promote tumor growth and angiogenesis, but the mechanism of mast cell activation is unclear. In earlier studies, we demonstrated that immunoglobulin free light chains (FLC) can trigger mast cells in an antigen-specific manner. Increased expression of FLC was observed within stroma of various human cancers including those of breast, colon, lung, pancreas, kidney and skin, and FLC expression co-localized with areas of mast cell infiltration. In a large cohort of breast cancer patients, FLC expression was shown associated with basal-like cancers with an aggressive phenotype. Moreover, lambda FLC was found expressed in areas of inflammatory infiltration and its expression was significantly associated with poor clinical outcome. Functional importance of FLCs was shown in a murine B16F10 melanoma model, where inhibition of FLC-mediated mast cell activation strongly reduced tumor growth. Collectively, this study identifies FLCs as a ligand in the pro-tumorigenic activation of mast cells. Blocking this pathway may open new avenues for the inhibition of tumor growth, while immunohistochemical staining of FLC may be helpful in the diagnosis and prognosis of cancer.

The matrikine N-α-PGP couples extracellular matrix fragmentation to endothelial permeability

The compartmentalization and transport of proteins and solutes across the endothelium is a critical biologic function altered during inflammation and disease, leading to pathology in multiple disorders. The impact of tissue damage and subsequent extracellular matrix (ECM) fragmentation in regulating this process is unknown. We demonstrate that the collagen-derived matrikine acetylated proline-glycine-proline (N-α-PGP) serves as a critical regulator of endothelial permeability. N-α-PGP activates human endothelial cells via CXC-chemokine receptor 2 (CXCR2), triggering monolayer permeability through a discrete intracellular signaling pathway. In vivo, N-α-PGP induces local vascular leak after subcutaneous administration and pulmonary vascular permeability after systemic administration. Furthermore, neutralization of N-α-PGP attenuates lipopolysaccharide-induced lung leak. Finally, we demonstrate that plasma from patients with acute respiratory distress syndrome (ARDS) induces VE-cadherin phosphorylation in human endothelial cells, and this activation is attenuated by N-α-PGP blockade with a concomitant improvement in endothelial monolayer impedance. These results identify N-α-PGP as a novel ECM-derived matrikine regulating paracellular permeability during inflammatory disease and demonstrate the potential to target this ligand in various disorders characterized by excessive matrix turnover and vascular leak such as ARDS.

Recovery of extracellular vesicles from human breast milk is influenced by sample collection and vesicle isolation procedures

Extracellular vesicles (EV) in breast milk carry immune relevant proteins and could play an important role in the instruction of the neonatal immune system. To further analyze these EV and to elucidate their function it is important that native populations of EV can be recovered from (stored) breast milk samples in a reproducible fashion. However, the impact of isolation and storage procedures on recovery of breast milk EV has remained underexposed. Here, we aimed to define parameters important for EV recovery from fresh and stored breast milk. To compare various protocols across different donors, breast milk was spiked with a well-defined murine EV population. We found that centrifugation of EV down into density gradients largely improved density-based separation and isolation of EV, compared to floatation up into gradients after high-force pelleting of EV. Using cryo-electron microscopy, we identified different subpopulations of human breast milk EV and a not previously described population of lipid tubules. Additionally, the impact of cold storage on breast milk EV was investigated. We determined that storing unprocessed breast milk at −80°C or 4°C caused death of cells present in breast milk, leading to contamination of the breast milk EV population with storage-induced EV. Here, an alternative method is proposed to store breast milk samples for EV analysis at later time points. The proposed adaptations to the breast milk storage and EV isolation procedures can be applied for EV-based biomarker profiling of breast milk and functional analysis of the role of breast milk EV in the development of the neonatal immune system.

Measurement of airway function using invasive and non-invasive methods in mild and severe models for allergic airway inflammation in mice

In this study a direct comparison was made between non-invasive and non-ventilated unrestrained whole body plethysmography (Penh) (conscious animals) and the invasive ventilated lung resistance (R_L) method (anesthetized animals) in both mild and severe allergic airway inflammation models. Mild inflammation was induced by intraperitoneal sensitization and aerosols of ovalbumin. Severe inflammation was induced by intraperitoneal sensitization using trinitrophenyl-ovalbumin, followed by intranasal challenges with IgE-allergen complexes. A significant increase in airway responsiveness to methacholine was observed in the mild inflammation group when R_L was measured. Significant changes in both R_L and Penh were observed in the severe inflammation groups. There was a significant increase in the number of inflammatory cells in the Broncho-Alveolar Lavage Fluid (BALF) in both the mild and severe inflammation animals. The enforced ventilation of the animals during the R_L measurement further increased the number of cells in the BALF. IL-2 and RANTES levels in the BALF were higher in the severe inflammation groups compared to the mild inflammation groups. Penh gave only reliable measurements during severe airway inflammation. Measuring R_L gave consistent results in both mild and severe allergic airway inflammation models however, ventilation induced an additional cell influx into the airways.

Targeting prolyl endopeptidase with valproic acid as a potential modulator of neutrophilic inflammation

A novel neutrophil chemoattractant derived from collagen, proline-glycine-proline (PGP), has been recently characterized in chronic obstructive pulmonary disease (COPD). This peptide is derived via the proteolytic activity of matrix metalloproteases (MMP's)-8/9 and PE, enzymes produced by neutrophils and present in COPD serum and sputum. Valproic acid (VPA) is an inhibitor of PE and could possibly have an effect on the severity of chronic inflammation. Here the interaction site of VPA to PE and the resulting effect on the secondary structure of PE is investigated. Also, the potential inhibition of PGP-generation by VPA was examined in vitro and in vivo to improve our understanding of the biological role of VPA. UV-visible, fluorescence spectroscopy, CD and NMR were used to determine kinetic information and structural interactions between VPA and PE. In vitro, PGP generation was significantly inhibited by VPA. In vivo, VPA significantly reduced cigarette-smoke induced neutrophil influx. Investigating the molecular interaction between VPA and PE showed that VPA modified the secondary structure of PE, making substrate binding at the catalytic side of PE impossible. Revealing the molecular interaction VPA to PE may lead to a better understanding of the involvement of PE and PGP in inflammatory conditions. In addition, the model of VPA interaction with PE suggests that PE inhibitors have a great potential to serve as therapeutics in inflammatory disorders.

Immunobiology of antigen-specific immunoglobulin free light chains in chronic inflammatory diseases

Mast cells are increasingly recognized as critical players in elicitation and maintenance of different inflammatory related disorders, like allergy, autoimmune diseases and cancer. Mast cells maturate within the tissue and are able to adapt to microenvironmental changes. Together with the ability to produce multiple pro- and anti-inflammatory mediators upon activation, mast cells are highly capable of exerting immunomodulatory functions. Cross-linking of receptor bound IgE is the best known mechanism of antigen-specific mast cell activation. In this review we focus on a different route of activation, via immunoglobulin free light chains (FLCs). Here, we describe current knowledge and concepts on FLCs based on preclinical models and data on human subjects, after briefly recapitulating early research findings on FLCs. Furthermore, because FLC research mainly focuses on mast cells, several mast cell mediated pathologies and mouse models for mast cell research will be discussed. Whether targeting of mast cells is beneficial for the treatment of specific disorders has to be addressed in future studies. Specific inhibition of FLC-mediated mast cell activation may be an interesting avenue to treat chronic inflammatory diseases.

Dendritic cells in pathogenesis of COPD

COPD (Chronic Obstructive Pulmonary Disease) is an important lung and airway disease which affects the lives of around 200 million people worldwide with an increasing incidence particularly in developing countries. The pathogenesis of COPD is based on the innate and adaptive inflammatory immune response to the inhalation of toxic particles and gases. Although cigarette smoking is the primary cause of this inflammation, many other environmental and occupational exposures contribute to the pathology of COPD. The immune inflammatory changes associated with COPD are linked to a tissue repair and remodeling process that increases mucus production and causes emphysematous destruction of the gas-exchanging surface of the lung. The inflamed airways of COPD patients contain several inflammatory cells including neutrophils, macrophages, T lymphocytes, and dendritic cells (DCs). Little is known about the relative contribution of DCs in the pathogenesis of COPD. However the number of DCs is changed in smokers and COPD patients and cigarette smoke (CS) induces the release of chemokines from DCs that play a role in the pathogenesis of COPD. In this review paper, an overview is presented on the role of DCs and their mediators in the pathogenesis of COPD. The activation of DCs and their signaling in response to CS will also be highlighted and discussed.

Antigen binding characteristics of immunoglobulin free light chains: crosslinking by antigen is essential to induce allergic inflammation

Beside the production of complete immunoglobulins IgG, IgE, IgA, IgM and IgD, consisting of tetrameric heterodimers of immunoglobulin heavy and light chains, B cells also secrete immunoglobulin free light chains (Ig-fLC). Previous studies showed that Ig-fLCs are able to induce immediate hypersensitivity reactions. It is apparent that recognition and binding of antigen are crucial steps in the onset of these inflammatory responses. In this study, the binding characteristics of Ig-fLC to antigen were further investigated using various biochemical approaches. In addition, we investigated whether antigen-mediated crosslinking of Ig-fLC is required to initiate allergic skin inflammation in vivo. Our study shows that binding of Ig-fLCs to antigen can be measured with different experimental setups. Surface plasmon resonance analysis showed real-time antigen binding characteristics. Specific antigen binding by Ig-fLCs was further detected using immunoblotting and ELISA. Using the ELISA-based assay, a binding affinity of 76.9±3.8 nM was determined for TNP-specific Ig-fLC. Antigen-induced ear swelling in mice passively sensitized with trinitrophenol-specific Ig-fLC was inhibited when multivalent antigen was combined with excess of monovalent antigen during challenge. We conclude that Ig-fLCs are able to interact with antigen, a prerequisite for antigen-specific cellular activation. In analogy to antigen-specific Fc receptor-induced mast cell activation, crosslinking of Ig-fLCs is necessary to initiate a local allergic response.

A relation between TGF-β and mast cell tryptase in experimental emphysema models

Chronic obstructive pulmonary disease (COPD) is a multicomponent disease characterized by emphysema and/or chronic bronchitis. The aim of this study was to investigate the effect of cigarette smoke exposure on mast cells and mast cell function in vitro and in vivo in order to get further insight in the role of mast cells in the pathogenesis of emphysema. Cigarette smoke conditioned medium (CSM) induced the expression of mast cell tryptase (MMCP-6) in primary cultured mast cells. This tryptase expression was caused by the CSM-stimulated production of TGF-β in culture and neutralization of TGF-β suppressed the CSM-induced expression of tryptase in mast cells. An increase in mast cell tryptase expression was also found in an experimental model for emphysema. Exposure of mice to cigarette smoke increased the number of mast cells in the airways and the expression of mast cell tryptase. In accordance with the in vitro findings, TGF-β in bronchoalveolar lavage fluid of smoke-exposed animals was significantly increased. Our study indicates that mast cells may be a source of TGF-β production after cigarette smoke exposure and that in turn TGF-β may change the tryptase expression in mast cells.

Non-digestible oligosaccharides reduce immunoglobulin free light-chain concentrations in infants at risk for allergy

Prebiotic oligosaccharides influence the intestinal microbiota and can positively modulate the infant's immune system. It was demonstrated that a special prebiotic mixture (Immunofortis(®)) of short-chain galacto-oligosaccharides (scGOS) and long-chain fructo-oligosaccharides (lcFOS) can reduce the cumulative incidence of atopic dermatitis (AD) in infants at risk for allergy as determined using the AD symptom score (SCORAD). Additionally, it was shown very recently that immunoglobulin free light-chain (Ig-fLC) might be involved in the pathophysiology of allergic disease. Increased Ig-fLC concentrations were found in patients suffering from AD, cow's milk allergy, allergic rhinitis, or asthma. In this study, the effect of supplementation of scGOS/lcFOS on the Ig-fLC plasma concentrations in infants at risk for allergy was assessed. The plasma kappa and lambda Ig-fLC concentrations were measured in a double-blind, placebo-controlled, randomized trial, in which infants at risk for developing allergic disease received a hypoallergenic whey formula containing 8 g/l of the scGOS/lcFOS mixture (n = 34) or maltodextrin as a placebo (n=40) for 6 months. After intervention, plasma samples were collected, and total plasma concentrations of lambda and kappa Ig-fLC were analyzed using ELISA. Total kappa and lambda Ig-fLC plasma concentrations were higher in infants suffering from AD when compared to infants without any sign of AD. In infants receiving the prebiotic mixture, the Ig-fLC levels were significantly lower compared to the placebo-fed infants (p<0.001). Interestingly, lambda Ig-fLC concentrations were positively correlated with total IgE (p<0.05). These data demonstrate for the first time that the specific scGOS/lcFOS mixture lowered kappa and lambda Ig-fLC plasma concentrations in infants at high risk for allergies when compared to infants receiving placebo formula. Because Ig-fLC concentrations were increased in infants suffering from AD, this may have contributed, at least in part, to the reduced incidence in AD as described previously. This suggests a possible role for Ig-fLC in the pathophysiology of AD in infants at risk for allergy development.

Toll-like receptor-9 triggering modulates expression of α-4 integrin on human B lymphocytes and their adhesion to extracellular matrix proteins

OBJECTIVE

The interaction of human B lymphocytes as recirculating cells with their microenvironment components including fibronectin is an instrumental process that directs their further responses in an inflammatory milieu or during their development in secondary lymphoid organs. Factors derived from extracellular environment, including those of pathogens, termed pathogen-associated molecular patterns, may have effects on this interaction, yet no study to date has addressed these effects. In this study, we explored the effect of Toll-like receptor 9 (TLR9) triggering on the interaction of normal B cells with fibronectin and collagen.

MATERIALS AND METHODS

The synthetic analog of TLR9 ligand, CpG-C, was used for stimulating the cells. The expression pattern of very late antigen-4 integrin was studied by fluorescence-activated cell sorting and Western blotting experiments, and cell adhesion was analyzed by fluorometric adhesion assay.

RESULTS

CpG at 0.5 μM upregulated fibronectin receptor (very late antigen-4) expression and cell adhesion, and increasing the CpG concentration did not have further effect. Blocking experiments with TLR9 signaling inhibitor, TTAGGG, anti-α4 antibody, and IκBα phosphorylation inhibitor, Bay 11-7082, confirmed that the CpG-induced induction level was TLR9 (partly), very late antigen-4, and nuclear factor-κB-mediated, respectively.

CONCLUSIONS

This study indicates that TLR9 triggering on B cells influences their interaction with extracellular matrix, which will be critical in modulating activation of these cells in conditions, such as infections, and gives a basic insight into the contribution of innate immunity elements in B-cell functional responses.

Decrease in immunoglobulin free light chains in patients with rheumatoid arthritis upon rituximab (anti-CD20) treatment correlates with decrease in disease activity

Objectives

Immunoglobulin (Ig) free light chains (FLCs) are short-lived B cell products that contribute to inflammation in several experimental disease models. In this study, FLC concentrations in inflamed joints of patients with rheumatoid arthritis (RA) as compared to patients with osteoarthritis were investigated. In addition, the relationship of FLCs and disease activity upon B cell depletion (rituximab) in patients with RA was studied.

Methods

Synovial fluid (SF) and tissue from patients with RA were analysed for local presence of FLCs using ELISA and immunohistochemistry. In addition, FLC concentrations were measured (at baseline, 3 and 6 months after treatment) in 50 patients with RA with active disease who were treated with rituximab. Changes in FLCs were correlated to changes in disease activity and compared to alterations in IgM, IgG, IgA, IgM-rheumatoid factor (RF) and IgG-anti-citrullinated protein antibody (ACPA) concentrations.

Results

FLCs were detected in synovial tissue from patients with RA, and high FLC concentrations were found in SF from inflamed joints, which positively correlate with serum FLC concentrations. Serum FLC concentrations significantly correlated with disease activity score using 28 joint counts, erythrocyte sedimentation rate (ESR) and C reactive protein, and changes in FLC correlated with clinical improvement after rituximab treatment. Moreover, effect of treatment on FLC concentrations discriminated clinical responders from non-responders, whereas IgM-RF and IgG-ACPA significantly decreased in both patient groups.

Conclusions

FLCs are abundantly present in inflamed joints and FLC levels correlate with disease activity. The correlation of FLC concentrations and disease activity indicates that FLCs may be relevant biomarkers for treatment response to rituximab in patients with RA and suggests that targeting FLC may be of importance in the therapy of RA.