High levels of neutralizing IL-6 autoantibodies in 0.1% of apparently healthy blood donors

Cytokine Autoantibodies Alter Gene Expression Profiles of Healthy Donors

Autoantibodies against cytokines (c-aAb) have been implicated in the pathophysiology of autoimmune diseases, and a variety of infections. In addition, several independent studies have detected elevated titers of c-aAb in the circulation of healthy individuals. To further understand their impact on immune responses, we measured c-aAb against IFN-α, IFN-γ, CSF2, IL-1α, IL-6, and IL-10 in the plasma of 1000 healthy individuals of the Milieu Intérieur (MI) cohort. Focusing on donors above a defined positive cut-off we observed significant age effects for c-aAb against IL-1α, but no major environmental or lifestyle associated factors were identified. Using TruCulture stimulation data from the MI cohort, we observed a strong association between induced IL-1α and c-aAb levels after LPS stimulation. For several other stimuli, c-aAb against IL-1α and IL-10 were associated with decreased or increased proinflammatory gene expression, respectively. Finally, TruCulture assays supplemented with plasma containing high-titer c-aAb showed a strong influence of anti-IFN-α and anti-IL-6 c-aAb on both baseline and induced gene expression. In summary, this study shows a widespread prevalence of anti-cytokine autoantibodies in healthy donors with impacts on diverse immune responses, suggesting a significant contribution of c-aAb to interindividual immune heterogeneity.

Autoantibodies targeting interferons and GM-CSF are associated with adverse outcome risk, comorbidities, and pathogen in community-acquired pneumonia

Introduction

Cytokine autoantibodies (c-aAb) have been associated with pulmonary diseases, including severe novel coronavirus disease 2019 (COVID-19) and pulmonary alveolar proteinosis. This study aimed to determine c-aAb association with community-acquired pneumonia (CAP) etiology (SARS-CoV-2, influenza, or bacteria) and c-aAb associations with CAP-related clinical outcomes and pulmonary comorbidities.

Methods

In a cohort of 665 patients hospitalized with CAP, c-aAb targeting interferon α (IFNα), IFNβ, IFNγ, interleukin-1α (IL-1α), IL-6, IL-10, and granulocyte-macrophage colony-stimulating factor (GM-CSF) were measured in plasma samples. Associations between c-aAb and baseline characteristics, pulmonary comorbidities, pathogen, intensive care unit (ICU) transferal, time to clinical stability, and mortality were estimated, with results stratified by sex.

Results

More men infected with SARS-CoV-2 were had high-titer type 1 IFN c-aAb compared to other pathogens. Among patients with CAP, asthma and bronchiectasis comorbidities were associated with high-titer GM-CSF c-aAb in men, and men with high-titer IFNβ c-aAb had increased odds for ICU transferal. High-titer IL-10 c-aAb were associated with faster clinical stability in women.

Conclusion

In men with CAP, various c-aAb-including type 1 IFN and GM-CSF c-aAb-were associated with adverse clinical events and comorbidities, whereas c-aAb targeting an autoinflammatory cytokine were associated with a positive outcome in women. This suggests that the potentially immunomodulatory effects of c-aAb depend on pathogen, autoantibody specificity, comorbidity, and sex.

The ouroboros of autoimmunity

Human autoimmunity against elements conferring protective immunity can be symbolized by the 'ouroboros', a snake eating its own tail. Underlying infection is autoimmunity against three immunological targets: neutrophils, complement and cytokines. Autoantibodies against neutrophils can cause peripheral neutropenia underlying mild pyogenic bacterial infections. The pathogenic contribution of autoantibodies against molecules of the complement system is often unclear, but autoantibodies specific for C3 convertase can enhance its activity, lowering complement levels and underlying severe bacterial infections. Autoantibodies neutralizing granulocyte-macrophage colony-stimulating factor impair alveolar macrophages, thereby underlying pulmonary proteinosis and airborne infections, type I interferon viral diseases, type II interferon intra-macrophagic infections, interleukin-6 pyogenic bacterial diseases and interleukin-17A/F mucocutaneous candidiasis. Each of these five cytokine autoantibodies underlies a specific range of infectious diseases, phenocopying infections that occur in patients with the corresponding inborn errors. In this Review, we analyze this ouroboros of immunity against immunity and posit that it should be considered as a factor in patients with unexplained infection.

Anti-cytokine autoantibodies: mechanistic insights and disease associations

Anti-cytokine autoantibodies (ACAAs) are increasingly recognized as modulating disease severity in infection, inflammation and autoimmunity. By reducing or augmenting cytokine signalling pathways or by altering the half-life of cytokines in the circulation, ACAAs can be either pathogenic or disease ameliorating. The origins of ACAAs remain unclear. Here, we focus on the most common ACAAs in the context of disease groups with similar characteristics. We review the emerging genetic and environmental factors that are thought to drive their production. We also describe how the profiling of ACAAs should be considered for the early diagnosis, active monitoring, treatment or sub-phenotyping of diseases. Finally, we discuss how understanding the biology of naturally occurring ACAAs can guide therapeutic strategies.

IL-6 Autoantibodies Predict Lower Platelet Counts and Altered Plasma Cytokine Profiles in Healthy Blood Donors: Results From the Danish Blood Donor Study

Cytokine-specific autoantibodies (c-aAb) represent a novel type of immune dysfunction. Though they have been detected in both patient cohorts and healthy individuals, and have immunomodulatory properties, the full extent of their influence remains unknown. Based on the critical role of several cytokines in thrombopoiesis, we investigated if there is an association between c-aAb and platelet variables in healthy individuals, with a specific focus on c-aAb against a known thrombopoietic cytokine, IL-6. Using platelet count and mean platelet volume in 3,569 healthy participants of the Danish Blood Donor Study as dependent variables, we performed a series of multivariate regression analyses using five cytokine autoantibodies, including IL-6 c-aAb, as independent variables. In men, high titers of IL-6 c-aAb were negatively associated with platelet counts (β = −24 ^*10⁹/l (95% confidence interval −43 to −6), p = 0.008) and positively associated with mean platelet volume (β = 0.4 fL (95% confidence interval 0.0–0.7) p = 0.043). These associations were exacerbated when adjusting for undetectable C-reactive protein levels, which we used as a proxy for c-aAb mediated IL-6 inhibition in vivo. Furthermore, in a smaller subgroup, individuals with high vs. low titer IL-6 c-aAb had different profiles of plasma IL-6, IL-10, TNFα and TPO, further suggesting a functional inhibition of IL-6 by high titers of circulating IL-6 c-aAb. We therefore speculate that in addition to their immunomodulatory potential IL-6 c-aAb may interfere with thrombopoiesis – directly or indirectly – under normal physiological conditions. This study is the first to suggest an influence of c-aAb on platelets in healthy individuals, beyond their apparent effects on immune competence.

Chronic inflammation markers and cytokine-specific autoantibodies in Danish blood donors with restless legs syndrome

Restless Legs Syndrome (RLS) is a neurological sensorimotor disorder negatively impacting sufferers’ quality of sleep and health-related quality of life. The pathophysiology of RLS is poorly understood and research focusing on the link between RLS and inflammation has been limited. Our study aimed to investigate whether chronic inflammation markers C-reactive protein (CRP) and soluble urokinase-type plasminogen activator receptor (suPAR), as well plasma levels of five different cytokine-specific autoantibodies (c-aAb), i.e. modulators of inflammation, associate with RLS in otherwise healthy individuals. CRP, suPAR and c-aAb were measured in plasma samples of participants from the Danish Blood Donor Study in 2010. Returning donors between 2015 and 2018 completed the validated Cambridge-Hopkins RLS-questionnaire for RLS assessment, resulting in datasets with RLS assessment and values for CRP (N = 3564), suPAR (N = 2546) and c-aAb (N = 1478). We performed logistic regression models using the CRP, suPAR or c-aAb as the independent variable and RLS status as the dependent variable, adjusted for appropriate covariates. Our study indicates that a high concentration of CRP is associated with RLS, while an increased probability of experiencing frequent RLS symptoms in those with an elevated plasma suPAR level appears to be mediated through lifestyle factors. We additionally report that a high titer of autoantibodies specific against the cytokine interferon-alpha was associated with RLS. Our results support the existence of links between systemic inflammation and RLS, though further RLS studies on CRP, suPAR and c-aAb in larger cohorts are warranted to confirm our findings and further reveal the hitherto underexplored links between RLS and inflammation.

Cytokine autoantibodies are stable throughout the haematopoietic stem cell transplantation course and are associated with distinct biomarker and blood cell profiles

Cytokine-specific autoantibodies (c-aAbs) represent an emerging field in endogenous immunodeficiencies, and the immunomodulatory potential of c-aAbs is now well documented. Here, we investigated the hypothesis that c-aAbs affects inflammatory, immunoregulatory and injury-related processes and hence the clinical outcome of haematopoietic stem cell transplantation (HSCT). C-aAbs against IL-1α, IL-6, IL-10, IFNα, IFNγ and GM-CSF were measured in 131 HSCT recipients before and after (days + 7, + 14, + 28) HSCT and tested for associations with 33 different plasma biomarkers, leukocyte subsets, platelets and clinical outcomes, including engraftment, GvHD and infections. We found that c-aAb levels were stable over the course of HSCT, including at high titres, with few individuals seeming to acquire high-titre levels of c-aAbs. Both patients with stable and those with acquired high-titre c-aAb levels displayed significant differences in biomarker concentrations and blood cell counts pre-HSCT and at day 28, and the trajectories of these variables varied over the course of HSCT. No clinical outcomes were associated with high-titre c-aAbs. In this first study of c-aAbs in HSCT patients, we demonstrated that high-titre levels of c-aAb may both persist and emerge in patients over the course of HSCT and may be associated with altered immune biomarkers and cell profiles.

Recurrent severe respiratory infections with low CRP secondary to autoimmune IL-6 deficiency

C reactive protein (CRP) is an inflammatory protein that is often used in conjunction with the clinical presentation of a patient to help with quantifying infection severity and measuring treatment response. We report the case of a patient who presented with severe pneumonias but had a suboptimal CRP response, later diagnosed as having an underlying immunodeficiency. This case exemplifies the need to consider immunodeficiency as an underlying pathophysiological cause in patients presenting with complicated and severe infections.

Usefulness of the IgA and IgG Responses to Macrophage Migration Inhibitory Factor for the Diagnosis of Tuberculosis

Serological tests offer the potential in order to improve the diagnosis of tuberculosis (TB). Macrophage migration inhibitory factor (MIF) plays a protective role in infection control in TB; however, to date, no studies on antibody responses to MIF have been reported. We measured immunoglobulin (Ig)A and IgG responses to MIF in individuals with either active tuberculosis (ATB; n = 65), latent tuberculosis (LTBI; n = 53), or in non-infected individuals (NI; n = 62). The QuantiFERON-TB Gold In-Tube (QFT-GIT) assay was used in order to screen for LTBI. The level of IgA against MIF was significantly lower in LTBI and ATB patients than in NI individuals, was significantly related to LTBI and ATB diagnosis, and it could discriminate between LTBI and ATB. In contrast, the level of IgG against MIF was significantly lower in LTBI patients than in NI individuals and was significantly related to LTBI diagnosis. Anti-MIF IgG levels were significantly lower in AFB-negative TB, minimal TB, and new ATB patients, than in the NI group. IgA and IgG levels against MIF both showed significant negative correlations with IFN-γ levels, as assessed using the QFT-GIT test. Although none of the antibodies could achieve high diagnostic predictive power individually, our results suggest the possibility of using IgA antibody responses to MIF in the diagnosis of LTBI and ATB.

Interleukin-6 signaling requires only few IL-6 molecules: Relation to physiological concentrations of extracellular IL-6

Introduction

The aim of this study was to give quantitative insight into the number of cytokine molecules needed to activate a target cell and relate this to the physiological consequences of the amounts of cytokines typically detectable in humans. As a model system blood interleukin‐6 (IL‐6) was chosen since this cytokine is one of the most studied and clinically monitored cytokines, and because of the tools for the present investigations such as fully bioactive iodinated recombinant IL‐6, cellular cytokine binding assays, and bioassays have been thoroughly validated.

Methods

The key intermediates of the basic equilibrium principles that govern cytokine binding and exchange were deduced and applied on concrete estimations of cellular and extracellular IL‐6 binding in the bloodstream based on experimental binding data and data from the literature. In parallel, in vitro cellular IL‐6 binding data was substantiated by paired measurements of IL‐6 bioactivity on IL‐6 sensitive B9 hybridoma cells.

Results

Blood leucocytes and B9 cells expressed 50 to 300, 10 to 20 picomolar affinity, IL‐6 binding sites per cell and at physiological concentrations of IL‐6 less than 10 IL‐6 molecules seemed to be bound to blood cells. Nonetheless, binding off as few as four IL‐6 molecules per cell seemed to result in statistically significant bioactivity, whereas binding of 16 IL‐6 molecules triggered extensive cellular responses.

Conclusion

Together, the estimations and the measurements support the notion that target cells with more than 100 bioactive cytokine receptors per cell, such as T cells and hepatocytes, are likely to be under steady and substantial cytokine‐induced endocrine activation.

Anti-Cytokine Autoantibodies in Systemic Lupus Erythematosus

Cytokine dysregulation is characteristic of systemic lupus erythematosus (SLE), a systemic autoimmune disease of considerable heterogeneity. Insights gained about the cytokine dysregulation in SLE have the potential for identifying patient subsets before the onset of clinical disease and during established disease. Clustering patients by cytokine and disease activity subsets is more informative than isolated cytokine studies, as both pro inflammatory and immunoregulatory cytokines contribute to the cytokine dysregulated state in SLE. Endogenous anti-cytokine autoantibodies (ACAAs) may be involved in the regulation of cytokine biology by reducing excessive production or by prolonging their half-life in the circulation through the formation of cytokine-antibody immune complexes. Although endogenous ACAAs may have deleterious effects such as contributing to immunodeficiency states, their role in the pathophysiology of autoimmune conditions such as SLE has yet to be clearly elucidated. The aim of the present article is to provide a focused review of the current knowledge of ACAAs in SLE.

Anti-IL6 Autoantibodies in an Infant With CRP-Less Septic Shock

Background: Interleukin-6 (IL-6) is a pleiotropic cytokine with a multitude of pro-inflammatory effects. Serum C-reactive protein (CRP) is an acute phase protein induced mainly by IL-6 in response to inflammatory conditions, particularly infection. The biological functions of CRP include opsonisation, induction of phagocytosis, complement activation, or chemotaxis enhancement. Factors interfering with IL-6-mediated recruitment of innate immune responses, such as the presence of anti-IL6 antibodies, may therefore compromise the host resistance to microbial pathogens. This has major implications for the use of IL-6-targeting biologics, such as tocilizumab or sarilumab in rheumatologic, immune dysregulation diseases, and cancer. Case presentation: 20-month-old Czech female developed severe septic shock with clinical and laboratory signs of systemic inflammation but no increase of CRP or IL-6. The offending pathogen was most likely Staphylococcus aureus, detected in a throat swab; the response to antibiotic treatment was prompt. A defect in the integrity of IL-6/CRP axis was suspected and verified by the detection of neutralizing IL-6 antibodies in the serum of the child. Conclusion: We report a first case of systemic bacterial infection in a patient with anti-IL6 autoantibodies. Disturbed IL-6 signaling, whether iatrogenic by targeted IL-6 blockade or endogenous due to the presence of autoantibodies against IL-6, represents a risk factor for increased infectious susceptibility. Patients with severe bacterial infection without elevation of CRP should be examined for the presence of anti-IL6 autoantibodies.

Prevalence and correlation of cytokine-specific autoantibodies with epidemiological factors and C-reactive protein in 8,972 healthy individuals: Results from the Danish Blood Donor Study

Natural cytokine-specific autoantibodies (c-aAb) have been measured in healthy and diseased individuals, and have been considered as both endogenous immune-regulators and pathogenic factors. Overall, the etiology and potential pathology of c-aAb are still undefined. To further characterize the sero-prevalence, predictors and consequences of high c-aAb levels, we performed the largest population-based study of c-aAb to date, using participants and epidemiological data from the Danish Blood Donor Study. Using a validated bead-based multiplex assay we assessed plasma levels of IL-1α, IL-6, IL-10, IFNα and GM-CSF-specific c-aAb in 8,972 healthy blood donors. Trace levels of at least one of the investigated c-aAb could be measured in 86% of the participants. The presence of high levels of potentially inhibitory c-aAb was generally associated with increasing age and male or female sex, depending on the c-aAb in question. A negative correlation between high levels of IL-6-specific c-aAb and plasma levels of C-reactive protein was observed, indicating cytokine-neutralizing levels of c-aAb in healthy blood donors. There was no substantial correlation between high levels of the five individual c-aAb investigated in this study. These data suggest that autoimmunity against endogenous cytokines is a relatively common phenomenon in healthy individuals, and that predictive factors for high, potentially neutralizing c-aAb levels vary depending on the cytokine in question, and may differ from predictors of general c-aAb presence.

Production of pure fractions of immunoglobulin G subclass autoantibodies against tumor necrosis factor

Autoantibodies directed against cytokines are important effector molecules regulating the biological activity of cytokines. There is experimental evidence indicating that autoantibodies belonging to different immunoglobulin G (IgG) subclasses may have different functional activity. The purpose of this work was to develop a protocol for the purification of fractions of IgG subclass antibodies directed against tumor necrosis factor (TNF). We developed a series of steps, including gel filtration, positive and negative affinity chromatography, and ultrafiltration, to achieve this goal. Our protocol purified IgG subclass autoantibodies directed against TNF from a human immunoglobulin preparation. The isolation of these anti-TNF autoantibodies will enable evaluation of the effect of TNF-specific antibodies on TNF biological activity. Our newly developed technique for purifying subclasses of anti-TNF autoantibodies may be important for both basic research on the functional activity of these autoantibodies and for clinical immunology.

IL-6-specific autoantibodies among APECED and thymoma patients

Introduction

Both autoimmune polyendocrinopathy‐candidiasis‐ectodermal dystrophy (APECED) and the rare thymoma patients with chronic mucocutaneous candidiasis (CMC) have neutralizing autoantibodies to Th17 cytokines and significant defects in production of IL‐22 and IL‐17F by their T cells. The cause of these defects is unknown. We hypothesized that they might result from autoimmunity against upstream cytokines normally responsible for generating and maintaining Th17 cells.

Methods

Luciferase immunoprecipitation (LIPS) was used to screen for autoantibodies to IL‐6, IL‐1β, TGF‐β3, IL‐21, and IL‐23 in patients with APECED or thymoma. We used Western blotting to assess the conformation‐dependence of the IL‐6 autoantibodies and flow cytometric analysis of intracellular phospho‐STAT3 induction to assess IL‐6‐neutralizing capacity in IgGs isolated from patient and control sera. We also used Luminex xMAP to measure serum cytokine levels.

Results

We found autoantibodies binding to conformational epitopes of IL‐6 in 19.5% of 41 patients with APECED and 12.5% of 104 with thymoma—especially in those with long disease durations. The autoantibodies were predominantly of IgG1 subclass and failed to neutralize IL‐6 activity. Notably, serum levels of the IL‐6 and IL‐17A cytokines were higher in anti‐IL‐6 seropositive than—negative APECED patients or healthy controls. We also detected autoantibody binding to IL‐23 in 27.9% of thymoma patients, resulting from cross‐recognition through the p40 subunit it shares with IL‐12.

Conclusions

IL‐6 and IL‐17A elevation in these seropositive patients suggests that antibody‐binding may protect IL‐6 from degradation and prolong its half‐life in vivo.

Mining the human autoantibody repertoire: isolation of potent IL17A-neutralizing monoclonal antibodies from a patient with thymoma

Anti-cytokine autoantibodies have been widely reported to be present in human plasma, both in healthy subjects and in patients with underlying autoimmune conditions, such as autoimmune polyendocrinopathy candidiasis ectodermal dystrophy (APECED) or thymic epithelial neoplasms. While often asymptomatic, they can cause or facilitate a wide range of diseases including opportunistic infections. The potential therapeutic value of specific neutralizing anti-cytokine autoantibodies has not been thoroughly investigated. Here we used mammalian cell display to isolate IL17A-specific antibodies from a thymoma patient with proven high-titer autoantibodies against the same. We identified 3 distinct clonotypes that efficiently neutralized IL17A in a cell-based in vitro assay. Their potencies were comparable to those of known neutralizing antibodies, including 2, AIN457 (secukinumab) and ixekizumab that are currently in clinical development for the treatment of various inflammatory disorders. These data clearly demonstrate that the human autoantibody repertoire can be mined for antibodies with high therapeutic potential for clinical development.

Protein microarrays: a new tool for the study of autoantibodies in immunodeficiency

Autoimmunity is highly coincident with immunodeficiency. In a small but growing number of primary immunodeficiencies, autoantibodies are diagnostic of a given disease and implicated in disease pathogenesis. In order to improve our understanding of the role of autoantibodies in immunodeficiencies and to discover novel autoantibodies, new proteomic tools are needed. Protein microarrays have the ability to screen for reactivity to hundreds to many thousands of unique autoantigens simultaneously on a single chip using minimal serum input. Here, we review different types of protein microarrays and how they can be useful in framing the study of primary and secondary immunodeficiencies.

Hyper-inflammation and skin destruction mediated by rosiglitazone activation of macrophages in IL-6 deficiency

Injury initiates recruitment of macrophages to support tissue repair; however, excessive macrophage activity may exacerbate tissue damage causing further destruction and subsequent delay in wound repair. Here we show that the peroxisome proliferation–activated receptor-γ agonist, rosiglitazone (Rosi), a medication recently reintroduced as a drug to treat diabetes and with known anti-inflammatory properties, paradoxically generates pro-inflammatory macrophages. This is observed in both IL-6-deficient mice and control wild-type mice experimentally induced to produce high titers of auto-antibodies against IL-6, mimicking IL-6 deficiency in human diseases. IL-6 deficiency when combined with Rosi-mediated upregulation of suppressor of cytokine signaling 3 leads to an altered ratio of nuclear signal transducer and activator of transcription 3/NF-κB that allows hyper-induction of inducible nitric oxide synthase (iNOS). Macrophages activated in this manner cause de novo tissue destruction, recapitulating human chronic wounds, and can be reversed in vivo by recombinant IL-6, blocking macrophage infiltration, or neutralizing iNOS. This study provides insight into an unanticipated paradoxical role of Rosi in mediating hyper-inflammatory macrophage activation significant for diseases associated with IL-6 deficiency.

Detection of anti-cytokine antibodies and their clinical relevance

Cytokines regulate many aspects of cell growth and differentiation and play pivotal roles in the orchestration of immune defence against invading pathogens. Though 'self' proteins, they are potentially immunogenic and can give rise to anti-cytokine autoantibodies (aCA). The main foci of the article are a critical summary of the various methodologies applied for detecting and measuring aCA and a broad review of studies of the occurrence, characterization and clinical relevance of aCA in normal healthy individuals, patients with autoimmune diseases or microbial infections and aCA in patients whose disease is treated with recombinant cytokine products. The need for technical and methodological improvement of assays, including validation and standardization, together with approaches to harmonize calculation and reporting of results is also discussed.

Immunoregulation by naturally occurring and disease-associated autoantibodies : binding to cytokines and their role in regulation of T-cell responses

The role of naturally occurring autoantibodies (NAbs) in homeostasis and in disease manifestations is poorly understood. In the present chapter, we review how NAbs may interfere with the cytokine network and how NAbs, through formation of complement-activating immune complexes with soluble self-antigens, may promote the uptake and presentation of self-molecules by antigen-presenting cells. Both naturally occurring and disease-associated autoantibodies against a variety of cytokines have been reported, including NAbs against interleukin (IL)-1α, IL-6, IL-8, IL-10, granulocyte-macrophage colony-stimulating factor, interferon (IFN)-α, IFN-β, IFN-γ, macrophage chemotactic protein-1 and IL-21. NAbs against a variety of other self-antigens have also been reported, and using thyroglobulin as an example we discuss how NAbs are capable of promoting uptake of immune complexes via complement receptors and Fc-receptors on antigen-presenting cells and thereby regulate T-cell activity. Knowledge of the influence of NAbs against cytokines on immune homeostasis is likely to have wide-ranging implications both in understanding pathogenesis and in treatment of many immunoinflammatory disorders, including a number of autoimmune and autoinflammatory diseases.

Beware of Antibodies to Dietary Proteins in “Antigen-specific” Immunoassays! Falsely Positive Anticytokine Antibody Tests Due to Reactivity with Bovine Serum Albumin in Rheumatoid Arthritis (The Swedish TIRA Project)

Objective.

To evaluate (1) to what extent sera from healthy subjects and patients with rheumatoid arthritis (RA) contain antibodies to bovine serum albumin (BSA); and (2) if anti-BSA antibodies interfere with results of enzyme-linked immunoassays (ELISA) containing BSA.

Methods.

The ELISA used was a previously developed in-house assay of autoantibodies to tumor necrosis factor (TNF). Anti-TNF and anti-BSA antibodies were analyzed by ELISA in 189 patients with early RA and 186 healthy blood donors. TNF preparations containing either BSA or human serum albumin (HSA) as carrier proteins were used as antigens in the anti-TNF assay. The presence and levels of antibodies were analyzed in relation to disease course and to the presence/absence of rheumatoid factor (RF).

Results.

In patients with RA, anti-TNF/BSA levels strongly correlated with anti-BSA levels (r = 0.81, p < 0.001), whereas anti-TNF/HSA did not (r = −0.09). Neither the presence nor the levels of anti-BSA in RA patients were associated with disease progression, and antibody levels were not significantly altered compared to controls (p = 0.11). IgG reactivity with TNF/HSA was neglible. In paired sera, preincubation with BSA abolished the anti-TNF/BSA reactivity. There were no indications of RF interference with anti-BSA or anti-TNF reactivity.

Conclusion.

Antibodies to BSA are common in patients with RA as well as in healthy individuals. Their presence does not seem to be associated with RA disease activity or disease course, but may severely interfere with ELISA containing BSA. The use of BSA as a “blocking agent” or carrier protein in immunoassays should therefore be avoided.

High avidity cytokine autoantibodies in health and disease: pathogenesis and mechanisms

Numerous reports have documented the presence of autoantibodies working against naturally occurring cytokines in humans in health and disease. In most instances, their physiological and pathophysiological significance remains unknown. However, recent advances in the methodologies for detecting cytokine autoantibodies and their application in research focused on specific disorders have shown that some cytokine autoantibodies play an important role in the pathogenesis of disease. Additionally, levels of cytokine autoantibodies may also correlate with disease severity and progression in certain infectious and autoimmune diseases but not in others. This suggests that cytokine-specific pathogenic differences exist. While multiple lines of evidence support the notion that high avidity cytokine autoantibodies are present and likely to be ubiquitous in healthy individuals, their potential physiological role, if any, is less clear. It is believed that they may function by scavenging pro-inflammatory cytokines and thereby inhibiting deleterious 'endocrine' effects, or by serving as carrier proteins, providing a 'reservoir' of inactive cytokines and thus modulating cytokine bioactivity. A central hypothesis is that sustained or repeated high-level exposure to cytokines triggers defects in T-cell tolerance, resulting in the expansion of existing cytokine autoantibody-producing B cells.

B-1 cells and naturally occurring antibodies: influencing the immunogenicity of recombinant human therapeutic proteins?

Recombinant human therapeutic proteins are increasingly being used to treat serious and life-threatening diseases like multiple sclerosis, diabetes mellitus, and cancer. An important side effect of these proteins is the development of antidrug antibodies, which can be neutralizing and thus interfere with the efficacy and safety of the drug. Some biophysical properties, for example, aggregation, also can initiate the immunogenic response to human therapeutics. Many other factors including patients' characteristics may influence this response. Besides induced antibodies, autoantibodies (i.e. naturally occurring antibodies [NAs]) against therapeutic relevant proteins in naïve patients are increasingly being identified. The role of autoreactive B cells and their escape from deletion, production of NAs and their pivotal function in the immune system, the dualistic role of B-1 cells in autoimmunity, and the influence of NAs on disease outcome and their possible impact on the efficacy of human therapeutics will be presented and discussed.

Isolation of human monoclonal antibodies by mammalian cell display

Due to their low immunogenicity in patients, humanized or fully human mAbs are becoming increasingly important for the treatment of a growing number of diseases, including cancer, infections, and immune disorders. Here, we describe a technology allowing for the rapid isolation of fully human mAbs. In contrast to previously described methods, B cells specific for an antigen of interest are directly isolated from peripheral blood mononuclear cells (PBMC) of human donors. Recombinant, antigen-specific single-chain Fv (scFv) libraries are generated from this pool of B cells and screened by mammalian cell surface display by using a Sindbis virus expression system. This method allows isolating antigen-specific antibodies by a single round of FACS. The variable regions (VRs) of the heavy chains (HCs) and light chains (LCs) are isolated from positive clones and recombinant fully human antibodies produced as whole IgG or Fab fragments. In this manner, several hypermutated high-affinity antibodies binding the Qbeta virus like particle (VLP), a model viral antigen, as well as antibodies specific for nicotine were isolated. All antibodies showed high expression levels in cell culture. The human nicotine-specific mAbs were validated preclinically in a mouse model. Thus, the technology presented here allows for rapid isolation of high-affinity, fully human antibodies with therapeutic potential from human volunteers.

Serum concentration of interleukin-6 is increased both in active and remission stages of pemphigus vulgaris

As most studies on pemphigus vulgaris (PV) pathogenesis concern its active stage, we aimed to evaluate the serum concentration of TNF-α, IL-1, and IL-6 in PV patients in clinical remission. The study group consisted of sera from 19 PV patients in active stage and from 24 patients in clinical remission. 19 sera taken from healthy subjects served as the controls. Serum IL-6 concentrations in PV active and PV remission group were significantly higher when compared to the controls (P < .05). In patients in active stage of PV, a significant correlation between serum IL-1 and IL-6 concentrations was found (r_P = 0.46; P < .05). We also found a negative correlation between TNF-α level and pemphigus antibodies titer in the patients from the remission group (r_S = −0.47303; P < .02). Our data suggest that IL-6 and TNF-α may be involved in maintaining immunological disturbances in remission stage of PV.

Recurrent staphylococcal cellulitis and subcutaneous abscesses in a child with autoantibodies against IL-6

We investigated an otherwise healthy patient presenting two episodes of staphylococcal cellulitis and abscesses, accompanied by high fever and biological signs of inflammation but, paradoxically, with no detectable increase in serum levels of C-reactive protein (CRP), an IL-6-responsive protein synthesized in the liver. Following in vitro activation of whole blood cells from the patient with multiple cytokines, TLR agonists, heat-killed bacteria, and mitogens, we observed a profound and specific impairment of IL-6 secretion. However, the patient's PBMCs, activated in the same conditions but in the absence of the patient's plasma, secreted IL-6 normally. The patient's serum contained high titers of IgG1 autoantibodies against IL-6, which specifically neutralized IL-6 production by control PBMCs as well as IL-6 responses in the human hepatocellular carcinoma cell line Hep3B. These anti-IL-6 autoantibodies were detected over a period of 4 years, in the absence of any other autoantibodies. Our results indicate that these Abs probably prevented an increase in CRP concentration during infection and that impaired IL-6-mediated immunity may have contributed to staphylococcal disease. Patients with severe bacterial infections and low serum CRP concentrations should be tested for anti-IL-6 autoantibodies, especially in the presence of other clinical and biological signs of inflammation.

Human monoclonal antibodies by immortalization of memory B cells

The administration of hyper immune sera to prevent or treat life-threatening infections is a remarkable milestone in medicine and biotechnology that has been achieved more than a century ago. Yet, the therapeutic use of monoclonal antibodies in this field has developed slowly over the last decades. Here we compare and contrast current methods to generate human monoclonal antibodies and highlight the advantages of exploiting the human antibody repertoire using a novel method that allows efficient immortalization and cloning of human memory B cells. This method, which has been successfully applied to isolate broadly neutralizing antibodies against SARS and H5N1 influenza viruses, is expected to accelerate the development of therapeutics in the field of infectious diseases not only by providing neutralizing antibodies for passive serotherapy, but also by generating relevant information for vaccine design.

Vaccination with IL-6 analogues induces autoantibodies to IL-6 and influences experimentally induced inflammation

IL-6 is involved in inflammation and a therapeutic target. 0.1% of Danish blood donors have nanomolar plasma concentrations of polyclonal, picomolar affinity and in vitro as well as in vivo neutralizing IgG autoantibodies to IL-6 (aAb-IL-6). Such donors are assumed to be severely IL-6 deficient; yet they appear healthy and do not exhibit overt clinical or laboratory abnormalities. We induced comparable levels of aAb-IL-6 in different mouse strains by vaccination with immunogenic IL-6 analogues. We observed that the induced aAb-IL-6 protected against collagen-induced arthritis and experimental allergic encephalitis. Furthermore, aAb-IL-6 carrying mice displayed increased plasma TNFalpha concentrations upon challenge with LPS. Taken together, induction of IL-6 autoantibodies was possible in different mouse strains. The autoantibodies influenced experimental inflammation. This immunotherapeutic principle might be a viable alternative in immune competent humans suffering from disorders driven by IL-6.

Anti-cytokine autoantibodies are ubiquitous in healthy individuals

Anti-cytokine autoantibodies in healthy individuals have been widely reported but the occurrence is variable and inconstant. We hypothesized that cytokine-binding in vivo may explain their variable and infrequent detection. Therefore, we focused on the detection of the cytokine-autoantibody complexes and found that anti-cytokine autoantibody to IL-2, IL-8, tumor necrosis factor-alpha, vascular endothelial growth factor and granulocyte-colony stimulating factor were present in all 15 individuals evaluated, while those to IL-3, osteopontin and macrophage-colony stimulating factor were not detected in anyone. Autoantibodies against IL-4, IL-6, IL-10, and interferon-gamma were variously detected. Thus, we discovered that anti-cytokine autoantibodies to multiple cytokines are ubiquitous in healthy individuals.

Transfusion-related inhibition of cytokines (TRICK). Experimental transfer of neutralizing autoantibodies to interleukin-6 by plasma transfusions

BACKGROUND

For some unknown reason humans may 'spontaneously' produce high amounts of neutralizing autoantibodies to a number of growth factors and cytokines. Reaching a certain high level the antibodies render the person cytokine deficient, mostly without overt clinical manifestations. The autoantibodies in question are detectable in normal immunoglobulin preparations and correspondingly in normal human plasma for transfusion. High affinity neutralizing autoantibodies to interleukin-6 (aAb-IL-6) are present in high titres in 0.1% of plasma from blood donors. Using aAb-IL-6 as a model we here report the first study addressing transfer of cytokine autoantibodies with blood components.

MATERIALS AND METHODS

We transferred high amounts of aAb-IL-6 to two patients suffering from end-stage disease of multiple myeloma. This was done by serial transfusions with normal human plasma highly positive for aAb-IL-6. We assessed recovery and kinetics of the transferred aAb-IL-6 and exposed how the recipients' plasma IL-6 bound to aAb-IL-6.

RESULTS

Free IL-6 was detectable in plasma of the recipients before transfusion. After the first transfusion IL-6 became immune complexed to aAb-IL-6 the molar plasma concentrations of which exceeded total IL-6 at least 500 times.

CONCLUSION

The observations signify that high amounts of neutralizing autoantibodies to cytokines (in this context aAb-IL-6) are occasionally transferred by transfusion. Although neither beneficial nor obvious detrimental effects of the plasmas were observed in this study our measurements evidently uncover a hitherto unknown form of transfusion-related immune modulation: transfusion-related inhibition of cytokines (TRICK). Depending on the cytokine autoantibody in question, the phenomenon might affect immune responses to infection and recovery after stem cell transplantation.

IL-6 levels predict disease variant and extent of organ involvement in patients with mastocytosis

Mastocytosis is often associated with organ involvement and hematological disorders. Patients may also exhibit elevated levels of plasma IL-6. To gain insight into the relevance of this observation, we correlated plasma levels of IL-6 and soluble IL-6 receptor (sIL-6R) with multiple disease parameters in 29 patients with mastocytosis. Mean plasma IL-6 levels were elevated in patients compared to healthy controls (P < 0.0001). Disease category significantly correlated with plasma IL-6 levels, as did severity of bone marrow pathology, organomegaly, and extent of skin involvement. In plasma, there was a positive correlation of IL-6 to total tryptase, alkaline phosphatase, IgM, white blood cell count, prothrombin time, partial thromboplastin time, and neutrophil numbers. There was an inverse correlation to hemoglobin. sIL-6R levels were not elevated. These observations demonstrate that IL-6 is a useful surrogate marker of severity of hematologic disease and suggest that IL-6 contributes to pathology.