The Biologic IRL201805 Alters Immune Tolerance Leading to Prolonged Pharmacodynamics and Efficacy in Rheumatoid Arthritis Patients.

A homologue of binding immunoglobulin protein/BiP-IRL201805 alters the function of immune cells in pre-clinical in vivo and in vitro studies. The aim of the study was to select biomarkers that clearly delineate between RA patients who respond to IRL201805 and placebo patients and reveal the immunological mode of action of IRL201805 driving the extended pharmacodynamics observed in responding patients. Biomarkers that distinguished between responding patients and placebo patients included downregulation of serum interferon-γ and IL-1ß; upregulation of anti-inflammatory mediators, serum soluble CTLA-4, and intracellular monocyte expression of IDO; and sustained increased CD39 expression on CD3+CD4+CD25hi CD127lo regulatory T cells. In the responding patients, selected biomarkers verified that the therapeutic effect could be continuous for at least 12 weeks post-infusion. In secondary co-culture, pre-infusion PBMCs cultured 1:1 with autologous PBMCs, isolated at later time-points during the trial, showed significantly inhibited IL-6 and IL-1ß production upon anti-CD3/CD28 stimulation demonstrating IRL201805 alters the function of immune cells leading to prolonged pharmacodynamics confirmed by biomarker differences. IRL201805 may be the first of a new class of biologic drug providing long-term drug-free therapy in RA.

Safety and patient response as indicated by biomarker changes to binding immunoglobulin protein in the phase I/IIA RAGULA clinical trial in rheumatoid arthritis.

OBJECTIVES: Binding immunoglobulin protein (BiP) is a human endoplasmic reticulum-resident stress protein. In pre-clinical studies it has anti-inflammatory properties due to the induction of regulatory cells. This randomized placebo-controlled, dose ascending double blind phase I/IIA trial of BiP in patients with active RA, who had failed accepted therapies, had the primary objective of safety. Potential efficacy was measured by DAS28-ESR and changes in biomarkers. METHODS: Twenty-four patients with active RA who had failed one or more DMARDs were sequentially assigned to three groups each of eight patients randomly allocated to receive placebo (two patients) or BiP (six patients), 1, 5 or 15 mg. Patients received a single i.v. infusion over 1 h and were observed as inpatients overnight. A 12-week follow-up for clinical, rheumatological and laboratory assessments for safety, efficacy (DAS28-ESR) and biomarker analysis was performed. RESULTS: No infusion reactions or serious adverse drug reactions were noted. Adverse events were evenly distributed between placebo and BiP groups with no BiP-related toxicities. Haematological, renal and metabolic parameters showed no drug-related toxicities. Remission was only achieved by patients in the 5 and 15 mg groups, and not patients who received placebo or 1 mg BiP. Good DAS28-ESR responses were achieved in all treatment groups. The BiP responding patients showed significantly lower serum concentrations of CRP, 2 weeks post-infusion compared with pre-infusion levels, and of VEGF and IL-8 from the placebo group. CONCLUSION: BiP (⩽15 mg) is safe in patients with active RA. Some patients had clinical and biological improvements in RA activity. BiP merits further study. TRIAL REGISTRATION: ISRCTN registry, http://isrctn.com, ISRCTN22288225 and EudraCT, https://eudract.ema.europa.eu, 2011-005831-19.

Immunoglobulin heavy-chain-binding protein (BiP): a stress protein that has the potential to be a novel therapy for rheumatoid arthritis.

Immunoglobulin heavy-chain-binding protein (BiP) or glucose-regulated protein 78 (Grp78) is a vital ubiquitous resident of the endoplasmic reticulum (ER). As an intracellular chaperone, BiP correctly folds nascent polypeptides within the ER and regulates the unfolded protein response ensuring protection of the cell from denatured protein and reinforcing its anti-apoptotic role, when the cell is under stress. Additionally, BiP is a member of the heat-shock protein (HSP) 70 family and, as a stress protein, is up-regulated by conditions of reduced oxygen and glucose. Cell stress induces surface expression and secretion of BiP. Consequently, BiP is detectable in several bodily fluids including serum, synovial fluid (SF) and oviductal fluid. However, as an extracellular protein, BiP has additional properties that are quite distinct from the intracellular functions. Extracellular BiP is immunoregulatory and anti-inflammatory causing development of tolerogenic dendritic cells (DCs), induction of regulatory T-cells, abrogation of osteoclast development and function, induction of anti-inflammatory cytokine production, including interleukin (IL)-10, IL-1 receptor antagonist and soluble tumour necrosis factor (TNF)-receptor type II, and attenuation of TNFα and IL-6. Together, these functions help drive the resolution of inflammation. Disease models of inflammatory arthritis have helped to demonstrate the novel mode of action of BiP in which the pharmacokinetics and pharmacodynamics are dissociated. The three murine models to be discussed each show BiP induced long-term therapeutic protection and therefore has potential for long-lasting drug-free therapy in rheumatoid arthritis (RA).

Autoantibodies to posttranslationally modified type II collagen as potential biomarkers for rheumatoid arthritis.

OBJECTIVE: Type II collagen (CII) posttranslationally modified by reactive oxygen species (ROS-CII) that are present in the inflamed joint is an autoantigen in rheumatoid arthritis (RA). The aim of this study was to investigate the potential use of anti-ROS-CII autoantibodies as a biomarker of RA. METHODS: CII was exposed to oxidants that are present in the rheumatoid joint. Autoreactivity to ROS-CII was assessed by enzyme-linked immunosorbent assays in synovial fluid (SF) and serum samples obtained from patients during various phases of RA. This group included disease-modifying antirheumatic drug (DMARD)-naive patients with early RA (n = 85 serum samples) and patients with established RA (n = 80 serum and 50 SF samples), who were categorized as either DMARD responders or DMARD nonresponders. Control subjects included anti-citrullinated protein antibody (ACPA)-positive patients with arthralgia (n = 58 serum samples), patients with osteoarthritis (OA; n = 49 serum and 52 SF samples), and healthy individuals (n = 51 serum samples). RESULTS: Reactivity to ROS-CII among DMARD-naive patients with early RA was significantly higher than that among patients with ACPA-positive arthralgia, patients with OA, and healthy control subjects (P < 0.0001), with 92.9% of serum samples from the patients with early RA binding to anti-ROS-II. There was no significant difference in anti-ROS-CII reactivity between ACPA-positive and ACPA-negative patients with RA, with 93.8% and 91.6% of serum samples, respectively, binding to ROS-CII. The sensitivity and specificity of binding to ROS-CII in patients with early RA were 92% and 98%, respectively. Among patients with established RA, serum reactivity in DMARD nonresponders was significantly higher than that in DMARD responders (P < 0.01); 58.3% of serum samples from nonresponders and 7.6% of serum samples from responders bound to HOCl-ROS, while the respective values for SF were 70% and 60%. In patients with longstanding RA, autoreactivity to ROS-CII changed longitudinally. CONCLUSION: Autoantibodies to ROS-CII have the potential to become diagnostic biomarkers of RA.

Pro-resolution immunological networks: binding immunoglobulin protein and other resolution-associated molecular patterns.

Appropriate regulation and subsequent resolution of acute inflammatory events is critical to the prevention of autoinflammatory diseases. Indeed, the chronic inflammation observed in diseases such as RA is at least partially consequent on the failure of endogenous immunoregulation. Current RA therapies (e.g. anti-TNF-α inhibitors and MTX) inhibit components of the inflammatory disease process without directly promoting the resolution of inflammation. We propose that the next generation of RA therapeutics will complement and augment endogenous immunoregulatory and pro-resolution immunological networks, thus promoting the definitive resolution of inflammation rather than temporary immunological control. Of particular interest with respect to this therapeutic approach is binding immunoglobulin protein [BiP; also known as glucose-regulated protein-78 (GRP78)], a member of the recently defined resolution-associated molecular pattern (RAMP) family of molecules. In this review, we consider the preclinical evidence from experiments in mouse and man that suggests BiP and other members of the RAMP family have the potential to herald a new generation of immunotherapeutics.

Binding immunoglobulin protein-treated peripheral blood monocyte-derived dendritic cells are refractory to maturation and induce regulatory T-cell development.

Binding immunoglobulin protein (BiP) has been shown previously to have immunomodulatory functions. Herein we investigated whether BiP could affect the differentiation of monocytes into dendritic cells (DCs) and thence the development of regulatory T cells. Peripheral blood monocyte-derived DCs were matured with lipopolysaccharide in the presence or absence of BiP. DC development and T-cell changes were monitored by flow cytometry and regulatory T-cell function was measured by uptake of tritiated thymidine. More BiP-treated DCs (DC((BiP))s) expressed amounts of intracellular indoleamine 2,3-dioxygenase (IDO) and cell surface leucocyte immunoglobulin-like receptor subfamily B member 1 (LILRB1), retained CD14 expression but down-regulated expression of human leucocyte antigen (HLA)-DR and CD86, and produced copious amounts of interleukin (IL)-10, when compared with control DCs. T cells co-cultured with DC((BiP))s developed regulatory function with increased surface expression of CD4(+) CD25(hi) CD27(hi) but with no concomitant increase in forkhead box P3 (Foxp3). These T cells also showed significantly higher levels of intracellular cytotoxic T-lymphocyte antigen (CTLA)-4. The latter could be inhibited by the presence of the IDO inhibitor 1 methyl tryptophan. The addition of neutralizing anti-IL-10 antibody or the specific mitogen-activated protein kinase (MAPK) p38 inhibitor SB203580 reversed the inhibition of DC differentiation by BiP. In conclusion, BiP is an immunomodulator able to arrest inflammation through induction of tolerogenic DCs and subsequent generation of T regulatory cells.

Real world long-term impact of intensive treatment on disease activity, disability and health-related quality of life in rheumatoid arthritis.

BACKGROUND: The emphasis on treating rheumatoid arthritis (RA) intensively reduces disease activity but its impact in routine care is uncertain. We evaluated temporal changes in disease activities and outcomes in a 10-year prospective observational cohort study of patients in routine care at one unit. METHODS: The Guy's and St Thomas' RA cohort was established in 2005. It involved most RA patients managed in this hospital. Clinical diagnoses of RA were made by rheumatologists. Patients were seen regularly in routine care. Each visit included measurement of disease activity scores for 28 joints (DAS28), health assessment questionnaire scores (HAQ) and EuroQol scores. Patients received intensive treatments targeting DAS28 remission. RESULTS: In 1693 RA patients mean DAS28 scores fell from 2005 to 15 by 11% from 4.08 (95% CI: 3.91, 4.25) in 2005 to 3.64 (3.34, 3.78); these falls were highly significant (p < 0.001). DAS28 components: swollen joint counts fell by 32% and ESR by 24%; in contrast tender joint counts and patient global assessments showed minimal or no reductions. The reduction in DAS28 scores was predominantly between 2005 and 2010, with no falls from 2011 onwards. Associated with falls in mean DAS28s, patients achieving remission increased (18% in 2005; 27% in 2015) and the number with active disease (DAS28 > 5.1) decreased (25% in 2005; 16% in 2015). In 752 patients seen at least annually for 3 years, persisting remission (68 patients) and intermittent remission (376 patients) were associated with less disability and better health related quality of life. Over time biologic use increased, but they were used infrequently in patients in persistent remission. CONCLUSIONS: Over 10 years an intensive management strategy in a routine practice setting increased combination DMARD and biologic use: disease activity levels declined; this association is in keeping with a causal relationship. Patients who achieved remission, even transiently, had better functional outcomes than patients never achieving remission.

Binding Immunoglobulin Protein (BIP) Inhibits TNF-α-Induced Osteoclast Differentiation and Systemic Bone Loss in an Erosive Arthritis Model.

OBJECTIVE: The association between inflammation and dysregulated bone remodeling is apparent in rheumatoid arthritis and is recapitulated in the human tumor necrosis factor transgenic (hTNFtg) mouse model. We investigated whether extracellular binding immunoglobulin protein (BiP) would protect the hTNFtg mouse from both inflammatory arthritis as well as extensive systemic bone loss and whether BiP had direct antiosteoclast properties in vitro. METHODS: hTNFtg mice received a single intraperitoneal administration of BiP at onset of arthritis. Clinical disease parameters were measured weekly. Bone analysis was performed by microcomputed tomography and histomorphometry. Mouse bone marrow macrophage and human peripheral blood monocyte precursors were used to study the direct effect of BiP on osteoclast differentiation and function in vitro. Monocyte and osteoclast signaling was analyzed by Western blotting, flow cytometry, and imaging flow cytometry. RESULTS: BiP-treated mice showed reduced inflammation and cartilage destruction, and histomorphometric analysis revealed a decrease in osteoclast number with protection from systemic bone loss. Abrogation of osteoclast function was also observed in an ex vivo murine calvarial model. BiP inhibited differentiation of osteoclast precursors and prevented bone resorption by mature osteoclasts in vitro. BiP also induced downregulation of CD115/c-Fms and Receptor Activator of NF-κB (RANK) messenger RNA and protein, causing reduced phosphorylation of the p38 mitogen-activated protein kinases, extracellular signal-regulated kinases 1/2 and p38, with suppression of essential osteoclast transcription factors, c-Fos and NFATc1. BiP directly inhibited TNF-α- or Receptor Activator of NF-κB Ligand (RANKL)-induced NF-κB nuclear translocation in THP-1 monocytic cells and preosteoclasts by the canonical and noncanonical pathways. CONCLUSION: BiP combines an anti-inflammatory function with antiosteoclast activity, which establishes it as a potential novel therapeutic for inflammatory disorders associated with bone loss.

BiP, an anti-inflammatory ER protein, is a potential new therapy for the treatment of rheumatoid arthritis.

The endoplasmic reticulum chaperone and stress protein BiP has hitherto been considered as having only crucial intracellular cell protective functions. However, we have shown that BiP can be present in the extracellular environment and that it binds to a putative but as yet uncloned cell surface receptor. It will stimulate human monocytes via this receptor to express a gene profile that is anti-inflammatory. It will generate T cells with a regulatory function from human peripheral blood most likely by altering dendritic cell development. Intravenous BiP will both prevent and treat ongoing collagen induced arthritis in the DBA/1 mouse. Part of the suppression of arthritis is linked to interleukin (IL)4 as BiP-specific lymph node and spleen cells from these mice secrete IL4, and BiP has no suppressive effect on collagen induced arthritis in IL4 knockout mice. Lymph node and spleen cells isolated from mice administered intravenous BiP will suppress arthritis when transferred intravenously into recipient arthritic mice without any further BiP having to be given. Thus, both in vitro work with human peripheral blood mononuclear cells and in vivo work in the collagen arthritis model lead to the conclusion that BiP induces regulatory cells. Finally, intravenous BiP will ablate the inflammatory cell infiltrate and inflammatory cytokine expression in rheumatoid synovial membrane tissue transplanted subcutaneously into SCID mice. The conclusion from all this experimental work is that BiP may be a novel therapy for the treatment of patients with rheumatoid arthritis.

Stress cytokines: pivotal proteins in immune regulatory networks; Opinion.

Stress proteins have three immunological regulatory functions: within the cell, on the cell membrane as signalling receptors, and in the extracellular environment as stress cytokines. They can activate the immune system by providing danger signals or they may downregulate immune and inflammatory responses. In addition, they can modulate immune responses by acting as chaperones for antigenic peptides while they themselves are processed and presented to T cells as self-peptides. We predict that the exploitation of the downregulatory properties of stress cytokines will have therapeutic applications in the treatment of human chronic inflammatory diseases, such as rheumatoid arthritis.

Autoantigens and immune pathways in rheumatoid arthritis.

Rheumatoid arthritis (RA) is a major systemic autoimmune disease. A plethora of putative autoantigens has been described by the reactivity of antibodies present in the sera of patients. Despite this there is little evidence implicating most of them in its pathogenesis. Autoantigens fall into two major groups: first, those that are associated with the joint, such as collagen type II, human chondrocyte glycoprotein 39, and proteoglycans, for which a pathogenic role is easily understood; and second, those proteins not associated with the joint. Of these there are three groups: (1) highly conserved foreign antigens with human homologues, such as heat shock proteins (HSPs), in which the initiating antigenic stimulus may be through infection; (2) post-translationally altered proteins, such as citrullinated filaggrin, to which autoantibodies show high specificity but low sensitivity for RA and immunoglobulin G; and (3) ubiquitous proteins, such as glucose-6-phosphate isomerase, p205, and HSPs secreted during stress, such as BiP. The mechanisms by which such ubiquitous antigens cause pathology predominantly in the joints are difficult to understand. Autoantibodies, such as rheumatoid factors, that form immune complexes resulting in activation of phagocytic cells or the complement system, may cause joint pathology by deposition in the joints. Such an explanation, however, is not available for all of these autoantigens. It is possible that pathology may be the outcome of disturbed immunoregulation.

B cell-directed therapy in rheumatoid arthritis--clinical experience.

Recent evidence has provided renewed insight into the role of B cells in the pathophysiology of rheumatoid arthritis (RA). The B cell surface antigen CD20 has been identified as an appropriate therapeutic target in the treatment of a number of immune-mediated conditions, including RA. Binding to CD20 results in depletion of B cells, with an associated improvement in symptoms, while leaving stem and plasma cells - which are devoid of this marker - unaffected. In a randomized double-blind controlled trial in patients with severe active RA who had had an inadequate response to disease modifying antirheumatic drugs (DMARD), a single short course of rituximab, an anti-CD20 chimeric monoclonal antibody, resulted in profound, long-lasting selective peripheral depletion of CD20+ B cells without compromising immunoglobulin levels, as well as significant and clinically meaningful improvements in symptoms of RA for up to 48 weeks without further treatment with rituximab. Rituximab added to existing methotrexate treatment was particularly effective and well tolerated, and provided the basis for further exploration of this promising alternative treatment approach in RA.

A New-Age for Biologic Therapies: Long-Term Drug-Free Therapy with BiP?

Heat shock proteins (HSPs) and other members of the much broader stress protein family have been shown to play important roles in coordinating multiple phases of immunological reactions; from facilitating immunological recognition, to promoting and regulating immunological responses and finally augmenting the resolution of inflammation and return to immunological homeostasis. In this review, we consider the challenges facing the stress protein field as we enter 2012; in particular we consider the role that HSPs and stress proteins may play in the initiation and termination of immunological responses. Special attention is afforded to the resolution-associated molecular pattern, binding immunoglobulin protein (BiP, also known as glucose regulated protein-78). We review the evidence that resolution-promoting proteins such as BiP may herald a new generation of biologics for inflammatory disease and reflect on the challenges of achieving clinical remission in rheumatoid arthritis with novel therapeutics and correlating clinical remission with immunological parameters of resolution of inflammation.

Binding immunoglobulin protein resolves rheumatoid synovitis: a xenogeneic study using rheumatoid arthritis synovial membrane transplants in SCID mice.

INTRODUCTION: Binding immunoglobulin protein (BiP) has previously shown powerful anti-inflammatory properties in the collagen-induced arthritis (CIA) model, where a single dose of BiP has proved to be both a long-term prophylactic and therapeutic. In both CIA and human in vitro studies, BiP induced regulatory T cells. The present investigation looked at the anti-inflammatory effect of BiP on inflamed human synovial tissue transplanted into severe combined immunodeficient mice (SCID), a chimaeric in vivo model previously used to test the efficacy of biologic therapies. METHODS: Rheumatoid arthritis synovial membrane (RASM) was engrafted into SCID mice. Following successful engraftment, mice were intravenously injected with BiP or human serum albumin in the presence or absence of anti-IL-10 mAb. Twelve days later the grafts were removed for analysis and human cytokines in the sera were quantified by ELISA. The extent of residual inflammatory cellular infiltrate in the synovial explants was determined by weight of the explants. RESULTS: The RASM transplants from mice treated with BiP showed visual reduction in cellular infiltrate and downregulation of all quantifiable features of inflammation as assessed by the Koizumi or Rooney histological criteria. Also downregulated were HLA-DR, CD86, IL-6 and TNFα expression as assessed by immunohistology. ELISA detected significantly less human IL-6 circulating in the BiP-treated mouse serum. After removal of transplanted tissue 12 days post administration of BiP, the RASM explants from the BiP-treated SCID mice weighed significantly less, indicating a suppression of tissue inflammation. Mice given concomitant neutralising anti-IL-10 antibody and BiP showed no such suppression. CONCLUSIONS: BiP has anti-inflammatory properties partially dependent on the downregulation of HLA-DR and co-stimulatory molecules and the predominant production of IL-10.

Functional and work outcomes improve in patients with rheumatoid arthritis who receive targeted, comprehensive occupational therapy.

OBJECTIVE: Work disability is a serious consequence of rheumatoid arthritis (RA). We conducted a 6-month, prospective randomized controlled trial comparing assessments of function, work, coping, and disease activity in employed patients with RA receiving occupational therapy intervention versus usual care. METHODS: Employed patients with RA with increased perceived work disability risk were identified by the RA Work Instability Scale (WIS; score >or=10). Patients were stratified into medium- (score >or=10 and <17) and high-risk (>or=17) groups, then randomized into occupational therapy or usual care groups. Assessments were conducted at baseline and 6 months. The primary outcome was the Canadian Occupational Performance Measure (COPM), a standardized patient self-report of function. Other outcomes included the disability index (DI) of the Health Assessment Questionnaire (HAQ); Disease Activity Score in 28 joints (DAS28); RA WIS; EuroQol Index; visual analog scales (VAS) for pain, work satisfaction, and work performance; and days missed/month. Independent sample t-tests and Mann-Whitney U tests were used. RESULTS: We recruited 32 employed patients with RA. At baseline the groups were well matched. At 6 months the improvement in the occupational therapy group was significantly greater than that in the usual care group for all functional outcomes (COPM performance P < 0.001, COPM satisfaction P < 0.001, HAQ DI P = 0.02) and most work outcomes (RA WIS [P = 0.04], VAS work satisfaction [P < 0.001], VAS work performance [P = 0.01]). Additionally, Arthritis Helplessness Index (P = 0.02), Arthritis Impact Measurement Scales II pain subscale (P = 0.03), VAS pain (P = 0.007), EuroQol Index (P = 0.02), EuroQol global (P = 0.02), and DAS28 (P = 0.03) scores significantly improved. CONCLUSION: Targeted, comprehensive occupational therapy intervention improves functional and work-related outcomes in employed RA patients at risk of work disability.

Treatment of murine collagen-induced arthritis by the stress protein BiP via interleukin-4-producing regulatory T cells: a novel function for an ancient protein.

OBJECTIVE: Following the demonstration that the stress protein, BiP, prevented induction of collagen-induced arthritis (CIA) in HLA-DRB*0101+/+ (HLA-DR1+/+) mice, we investigated the immunotherapeutic ability of BiP to suppress disease during the active phase of CIA in HLA-DR1+/+ and DBA/1 mice. METHODS: BiP was administered either subcutaneously or intravenously to DBA/1, HLA-DR1+/+, or interleukin-4 (IL-4)-knockout mice at the onset of arthritis. Immune cells were used in adoptive transfer studies or were restimulated in culture with BiP or type II collagen (CII). Proliferation and cytokine release were measured. In addition, serum anti-CII antibodies were measured by enzyme-linked immunosorbent assay. Disease progression was scored using a visual analog scale. RESULTS: BiP was successful in suppressing established CIA in HLA-DR1+/+ and DBA/1 mice. Serum levels of anticollagen IgG antibodies were reduced in BiP-treated mice. T cells from BiP-immunized mice produced Th2 cytokines, in particular, IL-4. Treatment with BiP was also shown to increase the production of CII-specific IL-5, IL-10, and interferon-gamma at the termination of the study. Development of severe CIA was prevented by the intravenous transfer of BiP-specific cells at the time of CIA induction in HLA-DR1+/+ mice or by transferring BiP-specific cells to DBA/1 mice at the onset of disease. BiP failed to ameliorate the development of CIA in IL-4-/-, HLA-DR1+/+ mice. CONCLUSION: These novel results show that BiP can suppress active CIA by the induction of regulatory cells that act predominantly via IL-4. Thus, BiP is a potential immunotherapeutic agent for the treatment of patients with rheumatoid arthritis.

Inhibition of antigen-presenting cell function and stimulation of human peripheral blood mononuclear cells to express an antiinflammatory cytokine profile by the stress protein BiP: relevance to the treatment of inflammatory arthritis.

OBJECTIVE: The stress protein and endoplasmic reticulum chaperone, immunoglobulin binding protein (BiP), is an autoantigen in rheumatoid arthritis (RA). Stress proteins, however, may have extracellular functions, mediated via cell surface receptors, that may include immunomodulatory functions. We sought to determine whether cell-free BiP is present in the synovial fluid (SF) of patients with RA and to further investigate the possible extracellular antiinflammatory and immunomodulatory properties of BiP in peripheral blood mononuclear cells (PBMCs) in vitro. METHODS: The presence of BiP in SF was established by Western blotting. PBMCs were stimulated with exogenous recombinant human BiP, and cytokine production and cell proliferation were measured in the presence and absence of cell signaling inhibitors or neutralizing anti-interleukin-10 (anti-IL-10) monoclonal antibody. Cytokine levels were quantified by enzyme-linked immunosorbent assay, cell proliferation by tritiated thymidine uptake, and cell surface molecule expression by flow cytometry. RESULTS: PBMCs responded to BiP with secretion of an antiinflammatory profile of cytokines. Although BiP stimulated the early production of tumor necrosis factor alpha (TNF alpha), the major cytokine induced was IL-10. Soluble TNF receptor II and IL-1 receptor antagonist secretion was also increased. Addition of SB203580, the MAPK p38 pathway inhibitor, partially inhibited the production of IL-10 and TNF alpha, whereas they were unaffected by the MAPK ERK-1/2 inhibitor PD98059. BiP also inhibited the recall antigen response by PBMCs to tuberculin purified protein derivative. Further investigation showed that incubation of monocytes in the presence of either BiP or IL-10 down-regulated CD86 and HLA-DR expression. The effect observed with IL-10 was transient compared with the long-lasting reduction induced by BiP. CONCLUSION: Extracellular BiP may stimulate immunomodulatory and antiinflammatory pathways, which are only partly due to the production of IL-10. These properties may be of relevance for the treatment of diseases such as RA.