Natural autoantibodies in the physiology and pathophysiology of the immune system

Autoantigen Exposure in Murine Fetuses Elicited Nonpathogenic Autoimmunity

BACKGROUND AND AIM

Autoimmunity refers to the presence of autoantibodies and autoreactive lymphocytes against the structural molecules of an individual's cells or tissues, known as self-antigens or autoantigens. It might exist in the absence of autoimmune disease. However, how autoimmunity develops remains a mystery, despite the discovery of autoantibodies in human cord blood.

METHODS

Murine fetuses on day 14 of gestation were subjected to intraperitoneal injection of murine thyroid peroxidase (TPO) peptides or collagen type II (CII) at graded doses via transuterine approach. Postnatally, the recipients were examined for autoantibodies by ELISA and autoreactive lymphocytes by in vitro incorporation of tritium and for the development of autoimmune thyroiditis or arthritis.

RESULTS

At one month of age, the recipients did not secrete significant levels of anti-TPO or CII IgG2a in sera until a dose of 0.5 µg TPO or 5.0 µg CII was injected in utero. Serum anti-TPO or CII IgG2a persisted for at least two to four months postnatally. In recipients with elevated autoantibodies, their lymphocytes also showed proliferative responses specifically to TPO or CII. However, the development of autoantibodies and autoreactive lymphocytes was not associated with inflammatory cell infiltration of thyroid glands or paw joints even though anti-TPO or CII IgG2a was enhanced by postnatal TPO or CII challenge.

CONCLUSION

Fetal exposure to free autoantigens could be immunogenic, shedding new light on the in utero origin of autoantibodies and autoreactive lymphocytes. The development of autoimmunity requires a threshold intensity of autoantigen exposure in the fetus.

Mendelian randomization and Bayesian model averaging of autoimmune diseases and Long COVID

Background

Following COVID-19, reports suggest Long COVID and autoimmune diseases (AIDs) in infected individuals. However, bidirectional causal effects between Long COVID and AIDs, which may help to prevent diseases, have not been fully investigated.

Methods

Summary-level data from genome-wide association studies (GWAS) of Long COVID (N = 52615) and AIDs including inflammatory bowel disease (IBD) (N = 377277), Crohn's disease (CD) (N = 361508), ulcerative colitis (UC) (N = 376564), etc. were employed. Bidirectional causal effects were gauged between AIDs and Long COVID by exploiting Mendelian randomization (MR) and Bayesian model averaging (BMA).

Results

The evidence of causal effects of IBD (OR = 1.06, 95% CI = 1.00-1.11, p = 3.13E-02), CD (OR = 1.10, 95% CI = 1.01-1.19, p = 2.21E-02) and UC (OR = 1.08, 95% CI = 1.03-1.13, p = 2.35E-03) on Long COVID was found. In MR-BMA, UC was estimated as the highest-ranked causal factor (MIP = 0.488, MACE = 0.035), followed by IBD and CD.

Conclusion

This MR study found that IBD, CD and UC had causal effects on Long COVID, which suggests a necessity to screen high-risk populations.

The Application of Nanovaccines in Autoimmune Diseases

Autoimmune diseases are diseases caused by the body's chronic immune responses to self-antigens and attacks on the host's own cells, tissues and organs. The dysfunction of innate immunity and adaptive immunity leads to the destruction of autoimmune tolerance, which is the most basic factor leading to pathogenesis. The optimal strategy for autoimmune diseases is to modify the host immune system to restore tolerance. The ideal effect of therapeutic autoimmune diseases is to eliminate the autoantigen-specific spontaneous immune response without interfering with the immune response against other antigens. Therapeutic nanovaccines that produce immune tolerance conform to this principle. Nanomaterials provide a platform for antigen loading and modification due to their unique physical and chemical properties. Nanovaccines based on nanomaterial technology can simultaneously enable antigens and adjuvants to be absorbed by immune cells and induce rapid and durable immunity. Nanovaccines have the advantages of being able to be designed and loaded and of better protecting antigens from premature degradation. Nanovaccines also have the ability to target specific tissues or cells through optimized design. We review the latest research progress of nanovaccines for autoimmune diseases and the design strategies of nanovaccines to promote the development of more effective nanovaccines for autoimmune diseases.

Natural autoimmunity in oligoarticular juvenile idiopathic arthritis

BACKGROUND

Oligoarticular juvenile idiopathic arthritis (oligo-JIA) is considered as an antigen-driven lymphocyte-mediated autoimmune disease. Natural antibodies (NAbs) are pre-immune antibodies produced in the absence of exogenous antigen stimulation, participating in both, innate and adaptive immunity. Considering their major immunoregulatory role in homeostasis and autoimmune pathogenesis, we designed this study to further elucidate their role in oligo-JIA pathogenesis.

METHODS

Seventy children with persistent oligo-JIA and 20 healthy matched controls were enrolled in the study. Serum IgM and IgA antibodies against human G-actin, human IgG F(ab΄)2 fragments and the hapten TriNitroPhenol (TNP) as well as the total concentration of serum IgM and IgA were measured by in-house enzyme-immunoassays. Kolmogorov-Smirnov normality test, Kruskal-Wallis H and Mann-Whitney tests were used to assess data distribution, and significant differences of non-parametric data between groups of the study. Backward regression analysis was used to analyze the effect of multiple factors (age, gender, disease activity, anti-nuclear antibody positivity, presence of uveitis) on continuous dependent variables (activities and activity/ concentration ratios of IgM and IgA NAbs).

RESULTS

The ratios of IgA anti-TNP, anti-actin and anti-F(ab΄)₂ levels to total serum IgA concentration were found to be significantly increased in patients with oligo-JIA compared to healthy subjects. Significantly elevated levels of IgM anti-TNP antibodies were also found in children with inactive oligo-JIA compared to those of children with active disease and of healthy controls. In the presence of anterior uveitis, IgM anti-TNP levels were significantly higher than in patients without uveitis or in healthy controls. Backward regression analysis revealed that the disease activity and the presence of anterior uveitis independently affect IgM anti-TNP levels.

CONCLUSUIONS

Our findings are in accordance with the hypothesis that NAbs contribute to the pathogenesis of autoimmune diseases and provide additional evidence that disturbances in natural autoimmunity may contribute to the as yet unclarified pathogenesis of oligo-JIA.

Temporal reproducibility of IgG and IgM autoantibodies in serum from healthy women

Autoantibodies are present in healthy individuals and altered in chronic diseases. We used repeated samples collected from participants in the NYU Women's Health Study to assess autoantibody reproducibility and repertoire stability over a one-year period using the HuProt array. We included two samples collected one year apart from each of 46 healthy women (92 samples). We also included eight blinded replicate samples to assess laboratory reproducibility. A total of 21,211 IgG and IgM autoantibodies were interrogated. Of those, 86% of IgG (n = 18,303) and 34% of IgM (n = 7,242) autoantibodies showed adequate lab reproducibility (coefficient of variation [CV] < 20%). Intraclass correlation coefficients (ICCs) were estimated to assess temporal reproducibility. A high proportion of both IgG and IgM autoantibodies with CV < 20% (76% and 98%, respectively) showed excellent temporal reproducibility (ICC > 0.8). Temporal reproducibility was lower after using quantile normalization suggesting that batch variability was not an important source of error, and that normalization removed some informative biological information. To our knowledge this study is the largest in terms of sample size and autoantibody numbers to assess autoantibody reproducibility in healthy women. The results suggest that for many autoantibodies a single measurement may be used to rank individuals in studies of autoantibodies as etiologic markers of disease.

Set Up for Failure: Pre-Existing Autoantibodies in Lung Transplant

Lung transplant patients have the lowest long-term survival rates compared to other solid organ transplants. The complications after lung transplantation such as primary graft dysfunction (PGD) and ultimately chronic lung allograft dysfunction (CLAD) are the main reasons for this limited survival. In recent years, lung-specific autoantibodies that recognize non-HLA antigens have been hypothesized to contribute to graft injury and have been correlated with PGD, CLAD, and survival. Mounting evidence suggests that autoantibodies can develop during pulmonary disease progression before lung transplant, termed pre-existing autoantibodies, and may participate in allograft injury after transplantation. In this review, we summarize what is known about pulmonary disease autoantibodies, the relationship between pre-existing autoantibodies and lung transplantation, and potential mechanisms through which pre-existing autoantibodies contribute to graft injury and rejection.

Overexpression of Endogenous Retroviruses and Malignancy Markers in Neuroblastoma Cell Lines by Medium-Induced Microenvironmental Changes

Neuroblastoma (NB) is the commonest solid tumor outside the central nervous system in infancy and childhood with a unique biological heterogeneity. In patients with advanced, metastasizing neuroblastoma, treatment failure and poor prognosis is often marked by resistance to chemo- or immunotherapy. Thus, identification of robust biomarkers seems essential for understanding tumor progression and developing effective therapy. Here, we have studied the expression of human endogenous retroviruses (HERV) as potential targets in NB cell lines during stem-cell medium-induced microenvironmental change. Quantitative PCR revealed that relative expression of the HERV-K family and HERV-W1 ENV were increased in all three NB cell lines after incubation in stem-cell medium. Virus transcriptome analyses revealed the transcriptional activation of three endogenous retrovirus elements: HERV-R ENV (ERV3-1), HERV-E1 and HERV-Fc2 ENV (ERVFC1-1). Known malignancy markers in NB, e.g. proto-oncogenic MYC or MYCN were expressed highly heterogeneously in the three investigated NB cell lines with up-regulation of MYC and MYCN upon medium-induced microenvironmental change. In addition, SiMa cells exclusively showed a phenotype switching from loosely-adherent monolayers to low proliferating grape-like cellular aggregates, which was accompanied by an enhanced CD133 expression. Interestingly, the overexpression of HERV was associated with a significant elevation of immune checkpoint molecule CD200 in both quantitative PCR and RNA-seq analysis suggesting tumor escape mechanism in NB cell lines after incubation in serum-free stem cell medium.

Autoimmune B Cell Repertoire in a Mouse Model of Sjögren's Syndrome

In genetically prone individuals, chronic immune activation may lead to expansion of autoreactive lymphocyte clones that can induce organ damage developing autoimmune disorders. Sjögren’s Syndrome (SjS) is a systemic chronic autoimmune disease that primarily affects exocrine glands. Despite the accumulated evidences of profound B-cell alterations of humoral immunity, the repertoire and development of B-cell autoreactivity in SjS remains to be determined. We hypothesize that SjS mice will have an increased frequency of self-reactive B cells with a progressive evolution to antigen-driven oligoclonality. Here, we study the B cell repertoire of NOD.H-2^h4 mice, a mouse model of spontaneous autoimmunity mimicking SjS without developing diabetes. A library of 168 hybridomas from NOD.H-2^h4 mice and 186 C57BL/6J splenocytes at different ages was created. The presence of mono or polyreactive autoantibodies to several antigens was evaluated by ELISA, and their staining patterns and cellular reactivity were tested by IFA and FACS. We observed a higher frequency of autoreactivity among B-cell clones from NOD.H-2^h4 mice as compared to wild-type mice. The presence of polyreactive and autoreactive IgG clones increased with mice age. Strikingly, all anti-Ro52 autoantibodies were polyreactive. No loss of polyreactivity was observed upon antibody class switching to IgG. There was a progression to oligoclonality in IgG B cells with mice aging. Our results indicate that in the NOD.H-2^h4 mouse model of SjS, IgG+ B cells are mainly polyreactive and might expand following an unknown antigen-driven positive selection process.

Immune Checkpoints, Inhibitors and Radionuclides in Prostate Cancer: Promising Combinatorial Therapy Approach

Emerging research demonstrates that co-inhibitory immune checkpoints (ICs) remain the most promising immunotherapy targets in various malignancies. Nonetheless, ICIs have offered insignificant clinical benefits in the treatment of advanced prostate cancer (PCa) especially when they are used as monotherapies. Current existing PCa treatment initially offers an improved clinical outcome and overall survival (OS), however, after a while the treatment becomes resistant leading to aggressive and uncontrolled disease associated with increased mortality and morbidity. Concurrent combination of the ICIs with radionuclides therapy that has rapidly emerged as safe and effective targeted approach for treating PCa patients may shift the paradigm of PCa treatment. Here, we provide an overview of the contextual contribution of old and new emerging inhibitory ICs in PCa, preclinical and clinical studies supporting the use of these ICs in treating PCa patients. Furthermore, we will also describe the potential of using a combinatory approach of ICIs and radionuclides therapy in treating PCa patients to enhance efficacy, durable cancer control and OS. The inhibitory ICs considered in this review are cytotoxic T-lymphocyte antigen 4 (CTLA4), programmed cell death 1 (PD1), V-domain immunoglobulin suppressor of T cell activation (VISTA), indoleamine 2,3-dioxygenase (IDO), T cell Immunoglobulin Domain and Mucin Domain 3 (TIM-3), lymphocyte-activation gene 3 (LAG-3), T cell immunoreceptor with Ig and ITIM domains (TIGIT), B7 homolog 3 (B7-H3) and B7-H4.

Autoantibody Signature in Cardiac Arrest

BACKGROUND

Cardiac arrest is a tragic event that causes 1 death roughly every 90 seconds worldwide. Survivors generally undergo a workup to identify the cause of arrest. However, 5% to 10% of cardiac arrests remain unexplained. Because cardiac arrhythmias underlie most cardiac arrests and increasing evidence strongly supports the involvement of autoantibodies in arrhythmogenesis, a large-panel autoantibody screening was performed in patients with cardiac arrest.

METHODS

This is an observational, cross-sectional study of patients from the Montreal Heart Institute hospital cohort, a single-center registry of participants. A peptide microarray was designed to screen for immunoglobulin G targeting epitopes from all known cardiac ion channels with extracellular domains. Plasma samples from 23 patients with unexplained cardiac arrest were compared with those from 22 patients with cardiac arrest cases of ischemic origin and a group of 29 age-, sex-, and body mass index-matched healthy subjects. The false discovery rate, least absolute shrinkage and selection operator logistic regression, and random forest methods were carried out jointly to find significant differential immunoglobulin G responses.

RESULTS

The autoantibody against the pore domain of the L-type voltage-gated calcium channel was consistently identified as a biomarker of idiopathic cardiac arrest (P=0.002; false discovery rate, 0.007; classification accuracies ≥0.83). Functional studies on human induced pluripotent stem cell-derived cardiomyocytes demonstrated that the anti-L-type voltage-gated calcium channel immunoglobulin G purified from patients with idiopathic cardiac arrest is proarrhythmogenic by reducing the action potential duration through calcium channel inhibition.

CONCLUSIONS

The present report addresses the concept of autoimmunity and cardiac arrest. Hitherto unknown autoantibodies targeting extracellular sequences of cardiac ion channels were detected. Moreover, the study identified an autoantibody signature specific to patients with cardiac arrest.

Serum Levels of Autoantibodies Against Extracellular Antigens and Neutrophil Granule Proteins Increase in Patients with COPD Compared to Non-COPD Smokers

Background

Chronic obstructive pulmonary disease (COPD) is a highly prevalent disease leading to irreversible airflow limitation and is characterized by chronic pulmonary inflammation, obstructive bronchiolitis and emphysema. Etiologically, COPD is mediated by toxic gases and particles, eg, cigarette smoke, while the pathogenesis of the disease is largely unknown. Several lines of evidence indicate a link between COPD and autoimmunity but comprehensive studies are lacking.

Methods

By using a protein microarray assaying more than 19,000 human proteins we determined in this study the autoantibody profiles of COPD and non-COPD smokers. The discovery cohort included 5 COPD patients under acute exacerbation (AECOPD) and 5 age- and gender-matched non-COPD smokers. One putative candidate autoantibody, anti-lactoferrin IgG, was further investigated by using immunoblotting with a large validation cohort containing 124 healthy controls, 92 patients with AECOPD and 52 patients with stable COPD.

Results

We show that i) autoantigens targeted by autoantibodies with higher titers in COPD patients were enriched in extracellular regions, while those with lower titers in COPD patients were enriched in intracellular compartments. ii) levels of IgG autoantibodies against many neutrophil granule proteins were significantly higher in COPD patients than in non-COPD smokers. Furthermore, increased levels of anti-lactoferrin antibodies in COPD patients were confirmed in a cohort with a large number of samples.

Conclusion

The comprehensive autoantibody profiles from COPD patients established in this study demonstrated for the first time a shift in the cellular localization of antigens targeted by autoantibodies in COPD.

The level of natural autoantibodies to IFN-gamma in varicella infection treated with antiviral drug Anaferon for children: A pilot study

Natural circulating antibodies (NAbs) to endogenous regulators have shown to be potential biomarkers in medicine. Due to the lack of reliable assays, only few of them have been well studied. To employ NAbs as biomarkers, an evaluation of changes over the course of a treatment is required. This paper describes our work to analyze the dynamics of NAbs titer to interferon-gamma (IFN-γ) among healthy children of different age and in patients with varicella infection receiving an antiviral drug Anaferon for children (AC, the API are highly diluted antibodies to IFN-γ) in comparison with placebo, and to correlate the findings with the treatment results. IFN-γ plays an essential role during varicella infection, and this fact causes the consequent increase of NAbs to IFN-γ level. The mean anti-IFN-γ NAbs level in the healthy volunteer group was 101 × 10³ U/ml (age: 0-15 years), which was significantly lower than the mean pre-treatment value in patients with varicella infection 167 × 10³ U/ml (age: 3-17 years). In the AC group, the NAbs level observed on days 5 and 10 decreased significantly to a level of 154 × 10³ U/ml, whereas in the placebo group it continued to rise in a time-dependent manner reaching 229 × 10³ U/ml on day 10. Our findings suggest that treatment with AC is characterized by "normalization" of the anti-IFN-γ NAbs levels in patients with varicella infection.

Antibody response against HERV-W in patients with MOG-IgG associated disorders, multiple sclerosis and NMOSD

Increased expression of the retroviruses of HERV-W family has been linked to multiple sclerosis (MS) pathophysiology; nothing is known at the moment about MOG-IgG associated disorders. We compared antibody response against HERV-W peptides among patients with MOG-IgG associated disorders, multiple sclerosis (MS) and aquaporin-4 (AQP4)-IgG positive neuromyelitis optica spectrum disorder (NMOSD). A total of 102 serum samples were retrospectively analyzed. Antibody reactivity against HERV-W env peptides was similar in MOG-IgG associated disorders and MS, but different from AQP4-IgG positive NMOSD. Our findings expand the diagnostic role of HERV-W antibodies to the spectrum of demyelinating disorders associated with MOG-IgG.

BP180 Autoantibodies Target Different Epitopes in Multiple Sclerosis or Alzheimer's Disease than in Bullous Pemphigoid

Neurologic patients have an increased risk for bullous pemphigoid (BP), in which autoantibodies target BP180, a cutaneous basement membrane protein also expressed in the brain. Here we show that 53.6% of sera from patients with multiple sclerosis (MS) (n = 56) had IgG reactivity against full-length BP180 in immunoblotting, while in BP180 non-collagenous 16A ELISA (n = 143), only 7.7% of MS samples studied were positive. Epitope mapping with 13 fusion proteins covering the entire BP180 polypeptide revealed that in MS and Alzheimer's disease (AD) patients, IgG autoantibodies target regions located in the intracellular and mid-extracellular parts of BP180, but not the well-known BP epitopes located in the non-collagenous 16A domain and the distal part of extracellular domain. In indirect immunofluorescence analysis, 8.1% of MS sera recognized the cutaneous basement membrane and in full-length BP180 ELISA analysis, 7.5% MS and AD sera were positive, indicating that these autoantibodies rarely recognize BP180 in its native conformation. Thus, in MS and AD patients, BP180 autoantibodies have a different epitope profile than in patients with BP, and seldom bind to native BP180. This explains the inability of these autoantibodies to cause skin symptoms. Our results suggest that the autoantibodies against BP180 alone are not sufficient to induce BP in MS and AD patients.

Identification of human endogenous retrovirus transcripts in Hodgkin Lymphoma cells

During the last decades, the prognosis for patients with Hodgkin Lymphoma (HL) has been steadily improved. Nevertheless, new and less toxic therapy strategies have to be developed especially for patients with advanced disease. The activation of human endogenous retroviruses (HERV) is suspected to occur in HL and therefore, HERV might represent interesting target structures. In order to identify transcribed HERV of the HERV-H and HERV-K families in HL we used a reverse transcription-polymerase chain reaction based cloning approach. In addition to unspliced HERV-H and HERV-K transcripts, we detected spliced HERV-K transcripts that matched genomic sequences with the expected splicing-donor and splicing-acceptor sites. Of particular interest was the expression of HERV-K18 related transcripts at the CD48 locus. Our data indicate transcriptional activity of several HERV loci in HL cells.

Natural antibodies - facts known and unknown

In contrast to adaptive antibodies, natural antibodies are present in a non-immunised organism from birth, and they do not include anti-Gal antibodies and/or anti-Gal natural antibodies, which are developed as a result of the effect of the α-Gal epitope and physiological flora. Natural antibodies are the first line of the organism’s defence before the formation of the immunity created via the stimulation of elements that determine specific and non-specific immunity. This is especially important in the case of infants. Despite the fact that natural antibodies differ in their function from adaptive antibodies, they are polyreactive and they detect autoantigens and new antigenic determinants. Natural antibodies are formed from the subpopulation of B lymphocytes, mainly B1 lymphocytes and B lymphocytes of the marginal zone. This phenomenon is supported by the fact that when the quantity of these cells in the organism decreases, which happens with age, the level of natural antibodies also decreases and the risk of illnesses of old age becomes higher. During ontogenesis, these antibodies participate in many physiological processes, including the “support” of the immune system and homeostasis, the prevention of inflammation, infections and other pathological states, such as autoimmune and cardiovascular diseases, or the process of carcinogenesis. The best known natural antibody is IgM, but the role of IgGs and IgAs is also considered important. Nowadays, many researchers also mention intravenous immunoglobulins, which are used in the treatment of numerous illnesses, and there are discussions on the possibility of increasing their potential if they were based on natural antibodies.

Linking autoimmunity to the origin of the adaptive immune system

In jawed vertebrates, the adaptive immune system (AIS) cooperates with the innate immune system (IIS) to protect hosts from infections. Although targeting non-self-components, the AIS also generates self-reactive antibodies which, when inadequately counter-selected, can give rise to autoimmune diseases (ADs). ADs are on the rise in western countries. Why haven’t ADs been eliminated during the evolution of a ∼500 million-year old system? And why have they become more frequent in recent decades? Self-recognition is an attribute of the phylogenetically more ancient IIS and empirical data compellingly show that some self-reactive antibodies, which are classifiable as elements of the IIS rather then the AIS, may protect from (rather than cause) ADs. Here, we propose that the IIS’s self-recognition system originally fathered the AIS and, as a consequence of this relationship, its activity is dampened in hygienic environments. Rather than a mere breakdown or failure of the mechanisms of self-tolerance, ADs might thus arise from architectural constraints.

Increased Steady-State Memory B Cell Subsets Among High-Risk Participants in an HIV Vaccine Trial

The success of an HIV vaccine will require induction of a protective immune response in the most at-risk populations. The increased incidence of HIV infection in high-risk populations is assumed to be primarily the result of more frequent exposure to the virus or a greater inoculum of the virus; however, underlying variations in immune homeostasis may also contribute to HIV susceptibility and potentially impact vaccine responses and those required for protection. As an effective humoral immune response is likely to be a critical component of a protective HIV vaccine, we evaluated the steady-state phenotypic profile of peripheral blood B cells by flow cytometry from participants in the HIV Vaccine Trials Network (HVTN) 203 Phase 2a HIV vaccine trial considered to be at higher risk and lower risk for HIV acquisition. Overall, high-risk participants exhibited increased frequency of unswitched IgM memory and activated switched IgD^-CD95⁺ memory B cells than low-risk participants. Most (93%) of the high-risk male participants were men who have sex with men who engaged in high-risk sexual behavior. High-risk males had a significantly increased frequency of CXCR3⁺ IgD^-CD95⁺ B cells than low-risk males. These results suggest that high-risk populations have altered B cell homeostasis. The increased frequency of activated and memory B cells may suggest increased immune activation in high-risk populations, which may contribute to possible differential responses to HIV vaccine strategies.

Recent advances in understanding autoimmune thyroid disease: the tallest tree in the forest of polyautoimmunity

Autoimmune thyroid disease (AITD) is often observed together with other autoimmune diseases. The coexistence of two or more autoimmune diseases in the same patient is referred to as polyautoimmunity, and AITD is the autoimmune disease most frequently involved. The occurrence of polyautoimmunity has led to the hypothesis that the affected patients suffer from a generalized dysregulation of their immune system. The present review summarizes recent discoveries unravelling the immunological mechanisms involved in autoimmunity, ranging from natural autoimmunity to disease-specific autoimmunity. Furthermore, the clinical grounds for considering AITD in a setting of polyautoimmunity are explored. A better understanding of these may pave the way for designing new treatment modalities targeting the underlying immune dysregulation when AITD appears in the context of polyautoimmunity.

A Special Connection between γδ T Cells and Natural Antibodies?

Natural antibodies (NAbs) play an important role in early host defense, autophagy and tissue remodeling, and in immune regulation. They arise spontaneously (without specific immunization), and are already present at birth. NAbs are produced by B1 B cells, MZ B cells and other B cell types. They include all major Ig subclasses but IgM antibodies are prevalent, especially early in development. NAbs may be poly-specific, recognize particular auto-antigens, or detect neo-determinants such as those exposed during apoptosis or generated by oxidation. NAbs do not require cognate T cell help but depend on soluble mediators produced by T cells. Our recent studies suggest that γδ T cells may have a special relationship with NAbs, and play a prominent role in their regulation, in part through the fine-tuning of IL-4 levels. The spontaneously activated state of these cells likely enables their cytokine production and other functions in the absence of external stimulation. Ontogenetically, the earlier arising γδ T cells are better positioned than αβ T cells to shape the developing repertoire of NAbs. Intriguingly, ligand specificities of NAbs and γδ T cell receptors appear to be overlapping, perhaps allowing γδ cognate help for certain NAb specificities. Via NAbs, γδ T cells could exert a regulatory influence on numerous processes in health and disease.

The Emerging Importance of Non-HLA Autoantibodies in Kidney Transplant Complications

Antibodies that are specific to organ donor HLA have been involved in the majority of cases of antibody-mediated rejection in solid organ transplant recipients. However, recent data show that production of non-HLA autoantibodies can occur before transplant in the form of natural autoantibodies. In contrast to HLAs, which are constitutively expressed on the cell surface of the allograft endothelium, autoantigens are usually cryptic. Tissue damage associated with ischemia-reperfusion, vascular injury, and/or rejection creates permissive conditions for the expression of cryptic autoantigens, allowing these autoantibodies to bind antigenic targets and further enhance vascular inflammation and renal dysfunction. Antiperlecan/LG3 antibodies and antiangiotensin II type 1 receptor antibodies have been found before transplant in patients with de novo transplants and portend negative long-term outcome in patients with renal transplants. Here, we review mounting evidence suggesting an important role for autoantibodies to cryptic antigens as novel accelerators of kidney dysfunction and acute or chronic allograft rejection.

Autopolyreactivity Confers a Holistic Role in the Immune System

In this review, we summarize and discuss some key findings from the study of naturally occurring autoantibodies. The B-cell compartment of the immune system appears to recognize almost all endogenous and environmental antigens. This ability is accomplished principally through autopolyreactive humoral and cellular immune receptors. This extended autopolyreactivity (1) along immunoglobulin gene recombination contributes to the immune system's ability to recognize a very large number of self and non-self constituents; and (2) generates a vast immune network that creates communication channels between the organism's interior and exterior. Thus, the immune system continuously evolves depending on the internal and external stimuli it encounters. Furthermore, this far-reaching network's existence implies activities resembling those of classical biological factors or activities that modulate the function of other classical biological factors. A few such antibodies have already been found. Another important concept is that natural autoantibodies are highly dependent on the presence or absence of commensal microbes in the organism. These results are in line with past and recent findings showing the fundamental influence of the microbiota on proper immune system development, and necessitate the existence of a host-microbe homeostasis. This homeostasis requires that the participating humoral and cellular receptors are able to recognize self-antigens and commensal microbes without damaging them. Autopolyreactive immune receptors expressing low affinity for both types of antigens fulfil this role. The immune system appears to play a holistic role similar to that of the nervous system.

Periodic acid-Schiff granules in the brain of aged mice: From amyloid aggregates to degenerative structures containing neo-epitopes

Brain ageing in mice leads to the progressive appearance and expansion of degenerative granular structures frequently referred as "PAS granules" because of their positive staining with periodic acid-Schiff (PAS). PAS granules are present mainly in the hippocampus, although they have also been described in other brain areas such as piriform and entorhinal cortices, and have been observed in other mammals than mice, like rats and monkeys. PAS granules have been identified as a wide range of brain deposits related to numerous neurodegenerative diseases, such as amyloid deposits, neurofibrillary tangles, Lafora bodies, corpora amylacea and polyglucosan bodies, and these identifications have generated controversy and particular theories about them. We have recently reported the presence of a neo-epitope in mice hippocampal PAS granules and the existence of natural IgM auto-antibodies directed against the neo-epitope in the plasma of the animals. The significance of the neo-epitope and the autoantibodies is discussed in this review. Moreover, we observed that the IgM anti-neo-epitope is frequently present as a contaminant in numerous commercial antibodies and is responsible of a considerable amount of false positive immunostainings, which may produce misinterpretations in the identification of the granules. Now that this point has been clarified, this article reviews and reconsiders the nature and physiopathological significance of these degenerative granules. Moreover, we suggest that neo-epitopes may turn into a useful brain-ageing biomarker and that autoimmunity could become a new focus in the study of age-related degenerative processes.

Recent Advances in Monoclonal Antibody Therapies for Multiple Sclerosis

INTRODUCTION

Multiple sclerosis (MS) is the most common chronic inflammatory, demyelinating disease of the CNS and results in neurological disability. Existing immunomodulatory and immunosuppressive approaches lower the number of relapses but do not cure or reverse existing deficits nor improve long-term disability in MS patients.

AREAS COVERED

Monogenic antibodies were described as treatment options for MS, however the immunogenicity of mouse antibodies hampered the efficacy of potential therapeutics in humans. Availability of improved antibody production technologies resulted in a paradigm shift in MS treatment strategies. In this review, an overview of immunotherapies for MS that use conventional monoclonal antibodies reactive to immune system and their properties and mechanisms of action will be discussed, including recent advances in MS therapeutics and highlight natural autoantibodies (NAbs) that directly target CNS cells.

EXPERT OPINION

Recent challenges for MS therapy are the identification of relevant molecular and cellular targets, time frame of treatment, and antibody toxicity profiles to identify safe treatment options for MS patients. The application of monoclonal antibody therapies with better biological efficacy associated with minimum side effects possesses huge clinical potential. Advances in monoclonal antibody technologies that directly target cells of nervous system may promote the CNS regeneration field from bench to bedside.

Human autoimmune diseases: a comprehensive update

There have been significant advances in our understanding of human autoimmunity that have led to improvements in classification and diagnosis and, most importantly, research advances in new therapies. The importance of autoimmunity and the mechanisms that lead to clinical disease were first recognized about 50 years ago following the pioneering studies of Macfarlane Burnett and his Nobel Prize-winning hypothesis of the 'forbidden clone'. Such pioneering efforts led to a better understanding not only of autoimmunity, but also of lymphoid cell development, thymic education, apoptosis and deletion of autoreactive cells. Contemporary theories suggest that the development of an autoimmune disease requires a genetic predisposition and environmental factors that trigger the immune pathways that lead, ultimately, to tissue destruction. Despite extensive research, there are no genetic tools that can be used clinically to predict the risk of autoimmune disease. Indeed, the concordance of autoimmune disease in identical twins is 12-67%, highlighting not only a role for environmental factors, but also the potential importance of stochastic or epigenetic phenomena. On the other hand, the identification of cytokines and chemokines, and their cognate receptors, has led to novel therapies that block pathological inflammatory responses within the target organ and have greatly improved the therapeutic effect in patients with autoimmune disease, particularly rheumatoid arthritis. Further advances involving the use of multiplex platforms for diagnosis and identification of new therapeutic agents should lead to major breakthroughs within the next decade.

The ups and downs of negative (and positive) selection of B cells

Central and peripheral tolerance checkpoints are in place to remove autoreactive B cell populations and prevent the development of autoimmunity. In this issue of the JCI, Pala and colleagues reveal that individuals with the X-linked immunodeficiency Wiskott-Aldrich syndrome (WAS) have opposite alterations at central and peripheral B cell checkpoints: a more stringent selection for central tolerance, resulting in reduced numbers of autoreactive cells at the emergent immature B cell stage, and a relaxed selection for peripheral tolerance, resulting in an increased frequency of autoreactive cells in the mature naive B cell compartment. Moreover, reinstatement of the WAS gene in these patients restored both B cell tolerance checkpoints. These results suggest that, in a normal situation, mature naive B cells undergo a positive selection step driven by self-antigens, kept in control by Tregs.

Autoimmunity in 2013

The peer-reviewed publications in the field of autoimmunity published in 2013 represented a significant proportion of immunology articles and grew since the previous year to indicate that more immune-mediated phenomena may recognize an autoimmune mechanism and illustrated by osteoarthritis and atherosclerosis. As a result, our understanding of the mechanisms of autoimmunity is becoming the paradigm for translational research in which the progress in disease pathogenesis for both tolerance breakdown and inflammation perpetuation is rapidly followed by new treatment approaches and clinical management changes. The similarities across the autoimmune disease spectrum outnumber differences, particularly when treatments are compared. Indeed, the therapeutics of autoimmune diseases are based on a growing armamentarium that currently includes monoclonal antibodies and small molecules which act by targeting molecular markers or intracellular mediators with high specificity. Among the over 100 conditions considered as autoimmune, the common grounds are well illustrated by the data reported for systemic lupus erythematosus and rheumatoid arthritis or by the plethora of studies on Th17 cells and biomarkers, particularly serum autoantibodies. Further, we are particularly intrigued by studies on the genomics, epigenetics, and microRNA at different stages of disease development or on the safe and effective use of abatacept acting on the costimulation of T and B cells in rheumatoid arthritis. We are convinced that the data published in 2013 represent a promising background for future developments that will exponentially impact the work of laboratory and clinical scientists over the next years.

Protective natural autoantibodies to apoptotic cells: evidence of convergent selection of recurrent innate-like clones

During murine immune development, recurrent B cell clones arise in a predictable fashion. Among these B cells, an archetypical clonotypic set that recognizes phosphorylcholine (PC) antigens and produces anti-PC IgM, first implicated for roles in microbial protection, was later found to become expanded in hyperlipidemic mice and in response to an increased in vivo burden of apoptotic cells. These IgM natural antibodies can enhance clearance of damaged cells and induce intracellular blockade of inflammatory signaling cascades. In clinical populations, raised levels of anti-PC IgM correlate with protection from atherosclerosis and may also downmodulate the severity of autoimmune disease. Human anti-PC-producing clones without hypermutation have been isolated that can similarly discriminate apoptotic from healthy cells. An independent report on unrelated adults has described anti-PC-producing B cells with IgM genes that have conserved CDR3 motifs, similar to stereotypic clonal sets of B cell chronic lymphocytic leukemia. Taken together, emerging evidence suggests that, despite the capacity to form an effectively limitless range of Ig receptors, the human immune system may often recurrently generate lymphocytes expressing structurally convergent B cell receptors with protective and homeostatic roles.

Antibodies to surface dopamine-2 receptor and N-methyl-D-aspartate receptor in the first episode of acute psychosis in children

BACKGROUND

The dopamine and glutamate hypotheses are well known in psychosis. Recently, the detection of autoantibodies against proteins expressed on the surface of cells in the central nervous system has raised the possibility that specific immune-mediated mechanisms may define a biological subgroup within psychosis, although no cohort of a first episode of psychosis in children has been investigated.

METHODS

Serum taken during the acute presentation of 43 children with first episode of psychosis and serum from 43 pediatric control subjects was assessed for the presence of immunoglobulin (Ig)G, IgM, or IgA antibodies to dopamine-2 receptor (D2R) and NR1 subunit of the N-methyl-D-aspartate receptor using a flow cytometry live cell-based assay and immunolabeling of murine primary neurons.

RESULTS

Using a cutoff of three SD above the control mean, serum antibodies to D2R or NR1 were detected in 8 of 43 psychotic patients but not detected in any of 43 control subjects (p < .001). Positive immunoglobulin binding to D2R was found in 3 of 43 psychosis patients (3 IgG, 1 IgM, 0 IgA) and to N-methyl-D-aspartate receptor in 6 of 43 patients (5 IgG, 1 IgM, 1 IgA). Specificity of antibody was confirmed by immunoaffinity purification and immunoabsorption. Significant differences in antibody binding to live, fixed, and fixed and permeabilized neurons were observed, confirming that only live cells can define surface epitope immunolabeling.

CONCLUSIONS

This is the first report of serum antibodies to surface D2R and NR1 in pediatric patients with isolated psychosis, which supports the hypothesis that a subgroup of patients may be immune-mediated.

Selection of apoptotic cell specific human antibodies from adult bone marrow

Autoreactive antibodies that recognize neo-determinants on apoptotic cells in mice have been proposed to have protective, homeostatic and immunoregulatory properties, although our knowledge about the equivalent antibodies in humans has been much more limited. In the current study, human monoclonal antibodies with binding specificity for apoptotic cells were isolated from the bone marrow of healthy adults using phage display technology. These antibodies were shown to recognize phosphorylcholine (PC)-associated neo-determinants. Interestingly, three of the four identified apoptotic cell-specific antibody clones were encoded by VH3 region rearrangements with germline or nearly germline configuration without evidence of somatic hypermutation. Importantly, the different identified antibody clones had diverse heavy chain CDR3 and deduced binding surfaces as suggested by structure modeling. This may suggest a potentially great heterogeneity in human antibodies recognizing PC-related epitopes on apoptotic cells. To re-construct the postulated structural format of the parental anti-PC antibody, the dominant clone was also expressed as a recombinant human polymeric IgM, which revealed a substantially increased binding reactivity, with dose-dependent and antigen-inhibitable binding of apoptotic cells. Our findings may have implication for improved prognostic testing and therapeutic interventions in human inflammatory disease.

Cellular targets and mechanistic strategies of remyelination-promoting IgMs as part of the naturally occurring autoantibody repertoire

Immunoglobulins with germline sequences occur in invertebrates and vertebrates and are named naturally occurring autoantibodies (NAbs). NAbs may target foreign antigens, self- or altered self-components and are part of the normal immunoglobulin repertoire. Accumulating evidence indicates that naturally occurring antibodies can act as systemic surveillance molecules, which tag, damaged or stressed cells, invading pathogens and toxic cellular debris for elimination by the immune system. In addition to acting as detecting molecules, certain types of NAbs actively signal in different cell types with a broad range of responses from induction of apoptosis in cancer cells to stimulation of remyelination in glial cells. This review emphasizes functions and characteristics of NAbs with focus on remyelination-promoting mouse and human antibodies. Human remyelination-promoting NAbs are potential therapeutics to combat a wide spectrum of disease processes including demyelinating diseases like multiple sclerosis. We will highlight the identified glycosphingolipid (SL) antigens of polyreactive remyelination-promoting antibodies and their proposed mechanism(s) of action. The nature of the identified antigens suggests a lipid raft-based mechanism for remyelination-promoting antibodies with SLs as most essential raft components. However, accumulating evidence also suggests involvement of other antigens in stimulation of remyelination, which will be discussed in the text.

Towards a liquid self: how time, geography, and life experiences reshape the biological identity

The conceptualization of immunological self is amongst the most important theories of modern biology, representing a sort of theoretical guideline for experimental immunologists, in order to understand how host constituents are ignored by the immune system (IS). A consistent advancement in this field has been represented by the danger/damage theory and its subsequent refinements, which at present represents the most comprehensive conceptualization of immunological self. Here, we present the new hypothesis of "liquid self," which integrates and extends the danger/damage theory. The main novelty of the liquid self hypothesis lies in the full integration of the immune response mechanisms into the host body's ecosystems, i.e., in adding the temporal, as well as the geographical/evolutionary and environmental, dimensions, which we suggested to call "immunological biography." Our hypothesis takes into account the important biological changes occurring with time (age) in the IS (including immunosenescence and inflammaging), as well as changes in the organismal context related to nutrition, lifestyle, and geography (populations). We argue that such temporal and geographical dimensions impinge upon, and continuously reshape, the antigenicity of physical entities (molecules, cells, bacteria, viruses), making them switching between "self" and "non-self" states in a dynamical, "liquid" fashion. Particular attention is devoted to oral tolerance and gut microbiota, as well as to a new potential source of unexpected self epitopes produced by proteasome splicing. Finally, our framework allows the set up of a variety of testable predictions, the most straightforward suggesting that the immune responses to defined molecules representing potentials antigens will be quantitatively and qualitatively quite different according to the immuno-biographical background of the host.

Notes on the epidemiology of multiple sclerosis, with special reference to dietary habits

A hypothesis, based primarily on the occurrence of multiple sclerosis (MS) in the Faroe Islands and supported by numerous analytical epidemiological studies, is described. It proposes that MS is caused by the interaction of a virus disease with intestinal pathology, e.g., infectious mononucleosis, and application of smoked and nitrate/nitrite-cured meat products in the diet during circumscribed time intervals. The biological mechanisms might involve a break of tolerance by an alteration of self within the central nervous system, by nitrophenylated compounds conjugated to animal tissue, in particular to proteins occurring in the central nervous system. Further research is needed.

Autoimmunity: from black water fever to regulatory function

Autoimmunity is a field that has only been around for a little over a century. Initially, it was thought that autoimmunity could not happen, that the body would never turn on itself (i.e. "horror autotoxicus"). It was only around the First World War that autoimmunity was recognized as the pathogenesis of various diseases, including rheumatoid arthritis. The discovery of Compound E led to successful treatment of patients with autoimmune diseases, but it was not till later that the adverse effects of this class of drugs were elucidated. The "modern" age of autoimmunity began around 1945 with the description of blackwater fever, and most of the subsequent research on hemolytic anemia and the role of an autoantibody in its pathogenesis led to a description of the anti-globulin reaction. The lupus erythematous (LE) cell was recognized in the mid-1940s by Hargreaves. His research carried on into the 1960s. Rheumatoid factor was also first described in the 1940s as yet another serum factor with activity against globulin-coated sheep red blood cells. The concept of autoimmunity really gained a foothold in the 1950s, when autoimmune thyroid disease and idiopathic thrombocytopenia were first described. Much has happened since then, and our understanding of autoimmunity has evolved now to include mechanisms of apoptosis, signaling pathway derangements, and the discovery of subsets of T cells with regulatory activity. The modern day study of autoimmunity is a fascinating area of research, and full understanding of the pathogenesis of autoimmune diseases is far from being completely elucidated.