Is IgG galactosylation the relevant factor for pregnancy-induced remission of rheumatoid arthritis?

Autoimmune pre-disease

Approximately 5% of the world-wide population is affected by autoimmune diseases. Overall, autoimmune diseases are still difficult to treat, impose a high burden on patients, and have a significant economic impact. Like other complex diseases, e.g., cancer, autoimmune diseases develop over several years. Decisive steps in the development of autoimmune diseases are (i) the development of autoantigen-specific lymphocytes and (often) autoantibodies and (ii) potentially clinical disease manifestation at a later stage. However, not all healthy individuals with autoantibodies develop disease manifestations. Identifying autoantibody-positive healthy individuals and monitoring and inhibiting their switch to inflammatory autoimmune disease conditions are currently in their infancy. The switch from harmless to inflammatory autoantigen-specific T and B-cell and autoantibody responses seems to be the hallmark for the decisive factor in inflammatory autoimmune disease conditions. Accordingly, biomarkers allowing us to predict this progression would have a significant impact. Several factors, such as genetics and the environment, especially diet, smoking, exposure to pollutants, infections, stress, and shift work, might influence the progression from harmless to inflammatory autoimmune conditions. To inspire research directed at defining and ultimately targeting autoimmune predisease, here, we review published evidence underlying the progression from health to autoimmune predisease and ultimately to clinically manifest inflammatory autoimmune disease, addressing the following 3 questions: (i) what is the current status, (ii) what is missing, (iii) and what are the future perspectives for defining and modulating autoimmune predisease.

The positive effect of pregnancy in rheumatoid arthritis and the use of medications for the management of rheumatoid arthritis during pregnancy

Rheumatoid arthritis (RA) is an autoimmune systemic inflammatory disorder that is mostly characterised by progressive symmetrical joint destruction, particularly in the wrist and fingers, while it may also affect additional joints and several organs, such as the skin, heart, blood vessels, and lungs. It is identified by raised anti-rheumatoid factor and anti-cyclic citrullinated peptide antibodies. The chemical mediators involved in the activity of RA are IL-1β, TNF-α, and IL-6. Pregnancy exerts a positive effect on RA that helps to modulate the disease condition. Different hypotheses are recommended to explain the ameliorating effect of pregnancy in RA. RA cannot be completely cured. The treatment goal is the attrition of pain and inflammation and the further progression of the disease. Long-term management of RA is carried out using disease-modifying antirheumatic drugs (DMARDs). Therapy of acute flares can be done with Non-steroidal anti-inflammatory drugs (NSAIDs) accompanied by ad interim usage of glucocorticoids. Biologic response modifiers are also available; they act by abolishing the activity of T- cells. However, it is necessary to select the correct treatment regimen when it comes to the management of RA in pregnancy.

Mechanisms determining the amelioration of rheumatoid arthritis in pregnancy: A systematic review

BACKGROUND

The phenomenon of pregnancy-induced remission of rheumatoid arthritis (RA) was first reported by Philip Hench in 1938. Despite extensive efforts, the underlying scientific basis has remained elusive. A number of different potential mechanisms have been investigated. We have undertaken a systematic review of the available peer-reviewed articles involving pregnant patients with RA in order to establish the depth of current scientific understanding of this important topic.

METHODS

This review was conducted according to guidelines of preferred reporting items for systematic reviews and meta-analyses. Studies were identified by a thorough search of multiple databases including Medline, PubMed and EMBASE. Search terms used were different combinations of the keywords: rheumatoid arthritis, inflammatory arthritis, pregnancy, mechanisms, disease activity, relapse and remission. Non-English language articles and studies that were not directly relevant were excluded. Two independent reviewers (CR and KA) screened the retrieved articles by reading the title and abstract to identify studies that addressed potential mechanisms determining RA activity in pregnancy. Articles were further refined after reading the full text. A data extraction sheet was developed for the purpose of this review and used by the independent reviewers.

RESULTS

After exclusion of irrelevant, duplicate and foreign language articles, a final total of 37 original articles were identified. The largest body of literature concerned glycosylation of immunoglobulins, with 9 published articles. There is evidence of an association between increasing levels of galactosylation of immunoglobulins and reduced RA disease activity in pregnancy. Other identified articles comprised 5 on cytokine changes in pregnancy, 5 on human leucocyte antigen (HLA) incompatibility, 5 on changes in peripheral blood mononuclear cell (PBMC) gene expression; 4 on changes in corticosteroids; 3 on pregnancy associated α2-glycoprotein; 2 on changes in rheumatoid factor (RF)/anti-citrullinated protein antibody (ACPA); and 1 each on microchimerism, gamma delta T cells, regulatory T cells, and mannose-binding lectin. The results of these studies were heterogenous and occasionally conflicting. Selected studies varied greatly in terms of population size, methodology and use of controls and disease activity assessments.

CONCLUSION

This systematic review has found that the cause of the pregnancy-induced amelioration of RA remains to be determined, despite extensive efforts. It is unclear which of the various transitory changes in pregnancy may be responsible for initiating downstream anti-inflammatory immunological mechanisms. We discuss limitations of the current literature and suggest areas for future study.

Abberant Immunoglobulin G Glycosylation in Rheumatoid Arthritis by LTQ-ESI-MS

Aberrant glycosylation has been observed in many autoimmune diseases. For example, aberrant glycosylation of immunoglobulin G (IgG) has been implicated in rheumatoid arthritis (RA) pathogenesis. The aim of this study is to investigate IgG glycosylation and whether there is an association with rheumatoid factor levels in the serum of RA patients. We detected permethylated N-glycans of the IgG obtained in serum from 44 RA patients and 30 healthy controls using linear ion-trap electrospray ionization mass spectrometry (LTQ-ESI-MS), a highly sensitive and efficient approach in the detection and identification of N-glycans profiles. IgG N-glycosylation and rheumatoid factor levels were compared in healthy controls and RA patients. Our results suggested that total IgG purified from serum of RA patients shows significantly lower galactosylation (p = 0.0012), lower sialylation (p < 0.0001) and higher fucosylation (p = 0.0063) levels compared with healthy controls. We observed a positive correlation between aberrant N-glycosylation and rheumatoid factor level in the RA patients. In conclusion, we identified aberrant glycosylation of IgG in the serum of RA patients and its association with elevated levels of rheumatoid factor.

Site-Specific N-Glycan Characterization of Grass Carp Serum IgM

Immunoglobulin M (IgM) is the major antibody in teleost fish and plays an important role in humoral adaptive immunity. The N-linked carbohydrates presenting on IgM have been well documented in higher vertebrates, but little is known regarding site-specific N-glycan characteristics in teleost IgM. In order to characterize these site-specific N-glycans, we conducted the first study of the N-glycans of each glycosylation site of the grass carp serum IgM. Among the four glycosylation sites, the Asn-262, Asn-303, and Asn-426 residues were efficiently glycosylated, while Asn-565 at the C-terminal tailpiece was incompletely occupied. A striking decrease in the level of occupancy at the Asn-565 glycosite was observed in dimeric IgM compared to that in monomeric IgM, and no glycan occupancy of Asn-565 was observed in tetrameric IgM. Glycopeptide analysis with liquid chromatography-electrospray ionization tandem mass spectrometry revealed mainly complex-type glycans with substantial heterogeneity, with neutral; monosialyl-, disialyl- and trisialylated; and fucosyl-and non-fucosyl-oligosaccharides conjugated to grass carp serum IgM. Glycan variation at a single site was greatest at the Asn-262 glycosite. Unlike IgMs in other species, only traces of complex-type and no high-mannose glycans were found at the Asn-565 glycosite. Matrix-assisted laser desorption ionization analysis of released glycans confirmed the overwhelming majority of carbohydrates were of the complex-type. These results indicate that grass carp serum IgM exhibits unique N-glycan features and highly processed oligosaccharides attached to individual glycosites.

Sialylated Autoantigen-Reactive IgG Antibodies Attenuate Disease Development in Autoimmune Mouse Models of Lupus Nephritis and Rheumatoid Arthritis

Pro- and anti-inflammatory effector functions of IgG antibodies (Abs) depend on their subclass and Fc glycosylation pattern. Accumulation of non-galactosylated (agalactosylated; G0) IgG Abs in the serum of rheumatoid arthritis and systemic lupus erythematosus (SLE) patients reflects severity of the diseases. In contrast, sialylated IgG Abs are responsible for anti-inflammatory effects of the intravenous immunoglobulin (pooled human serum IgG from healthy donors), administered in high doses (2 g/kg) to treat autoimmune patients. However, whether low amounts of sialylated autoantigen-reactive IgG Abs can also inhibit autoimmune diseases is hardly investigated. Here, we explore whether sialylated autoantigen-reactive IgG Abs can inhibit autoimmune pathology in different mouse models. We found that sialylated IgG auto-Abs fail to induce inflammation and lupus nephritis in a B cell receptor (BCR) transgenic lupus model, but instead are associated with lower frequencies of pathogenic Th1, Th17 and B cell responses. In accordance, the transfer of small amounts of immune complexes containing sialylated IgG Abs was sufficient to attenuate the development of nephritis. We further showed that administration of sialylated collagen type II (Col II)-specific IgG Abs attenuated the disease symptoms in a model of Col II-induced arthritis and reduced pathogenic Th17 cell and autoantigen-specific IgG Ab responses. We conclude that sialylated autoantigen-specific IgG Abs may represent a promising tool for treating pathogenic T and B cell immune responses in autoimmune diseases.

Novel Concepts of Altered Immunoglobulin G Galactosylation in Autoimmune Diseases

The composition of the conserved N297 glycan in immunoglobulin G (IgG) has been shown to affect antibody effector functions via C1q of the complement system and Fc gamma receptors (FcγR) on immune cells. Changes in the general levels of IgG-glycoforms, such as lowered total IgG galactosylation observed in many autoimmune diseases have been associated with elevated disease severity. Agalactosyslated IgG has therefore been regarded and classified by many as pro-inflammatory. However, and somewhat counterintuitively, agalactosylation has been shown by several groups to decrease affinity for FcγRIII and decrease C1q binding and downstream activation, which seems at odds with this proposed pro-inflammatory nature. In this review, we discuss these circumstances where altered IgG galactosylation/glycosylation is found. We propose a novel model based on these observations and current biochemical evidence, where the levels of IgG galactosylation found in the total bulk IgG affect the threshold required to achieve immune activation by autoantibodies through either C1q or FcγR. Although this model needs experimental verification, it is supported by several clinical observations and reconciles apparent discrepancies in the literature, and suggests a general mechanism in IgG-mediated autoimmune diseases.

Sweet but dangerous - the role of immunoglobulin G glycosylation in autoimmunity and inflammation

Glycosylation is well-known to modulate the functional capabilities of immunoglobulin G (IgG)-mediated cellular and humoral responses. Indeed, highly sialylated and desialylated IgG is endowed with anti- and pro-inflammatory activities, respectively, whereas fully deglycosylated IgG is a rather lame duck, with no effector function besides toxin neutralization. Recently, several studies revealed the impact of different glycosylation patterns on the Fc part and Fab fragment of IgG in several autoimmune diseases, including systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). Here, we provide a synoptic update summarizing the most important aspects of antibody glycosylation, and the current progress in this field. We also discuss the therapeutic options generated by the modification of the glycosylation of IgG in a potential treatment for chronic inflammatory diseases.

Glucocorticoid receptor gene polymorphisms and disease activity during pregnancy and the postpartum period in rheumatoid arthritis

INTRODUCTION

The mechanism underlying the spontaneous improvement of rheumatoid arthritis (RA) during pregnancy and the subsequent postpartum flare is incompletely understood, and the disease course varies widely between pregnant RA patients. In pregnancy, total and free levels of cortisol increase gradually, followed by a postpartum decrease to prepregnancy values. The glucocorticoid receptor (GR) polymorphisms BclI and N363S are associated with relatively increased glucocorticoid (GC) sensitivity, whereas the 9β and ER22/23EK polymorphisms of the GR gene are associated with a relatively decreased GC sensitivity. We examined the relation between the presence of these GR polymorphisms and level of disease activity and disease course of RA during pregnancy and postpartum.

METHODS

We studied 147 participants of the PARA study (Pregnancy-Induced Amelioration of Rheumatoid Arthritis study), a prospective study investigating the natural improvement during pregnancy and the postpartum flare in women with RA. Patients were visited, preferably before pregnancy, at each trimester and at three postpartum time points. On all occasions, disease activity was scored by using DAS28. All patients were genotyped for the GR polymorphisms BclI, N363S, 9β, and ER22/23EK and divided in groups harboring either polymorphisms conferring increased GC sensitivity (BclI and N363S; GC-S patients) or polymorphisms conferring decreased GC sensitivity (9β or 9β + ER22/23EK; GC-I patients). Data were analyzed by using a mixed linear model, comparing GC-S patients with GC-I patients with respect to improvement during pregnancy and the postpartum flare. The cumulative disease activity was calculated by using time-integrated values (area under the curve, AUC) of DAS28 in GC-I patients versus GC-S patients. Separate analyses were performed according to the state of GC use.

RESULTS

GC-S patients treated with GC had a significantly lower AUC of DAS28 in the postpartum period than did GC-I patients. This difference was not observed in patients who were not treated with GCs. During pregnancy, GC-S and GC-I patients had comparable levels of disease activity and course of disease.

CONCLUSIONS

Differences in relative GC sensitivity, as determined by GR polymorphisms, are associated with the level of disease activity in the postpartum period in GC-treated patients, but they do not seem to influence the course of the disease per se.

Pregnancy and rheumatoid arthritis: insights into the immunology of fetal tolerance and control of autoimmunity

It has long been recognized that symptoms and signs of rheumatoid arthritis (RA) frequently improve spontaneously during pregnancy, only to flare postpartum. Although the mechanisms behind this phenomenon remain poorly understood, there is growing interest in the immunologic changes that occur during healthy pregnancy as a possible explanation. Because the maternal immune system must adapt during pregnancy to accept the semi-allogeneic fetus, it has been hypothesized that these natural changes induced by pregnancy on maternal immune regulatory cells may have the additional benefit of controlling the immunopathology driving disease activity in RA. Here, we review our current understanding on the effects of pregnancy on RA and highlight some of the recent literature related to advancing our understanding on the immunology of pregnancy as well as the immunologic changes in RA during pregnancy.

Fetal and Neonatal Illnesses Caused or Influenced by Maternal Transplacental IgG and/or Therapeutic Antibodies Applied During Pregnancy

The human fetus is protected by the mother’s antibodies. At the end of the pregnancy, the concentration of maternal antibodies is higher in the cord blood, than in the maternal circulation. Simultaneously, the immune system of the fetus begins to work and from the second trimester, fetal IgM is produced by the fetal immune system specific to microorganisms and antigens passing the maternal-fetal barrier. The same time the fetal immune system has to cope and develop tolerance and T_REG cells to the maternal microchimeric cells, latent virus-carrier maternal cells and microorganisms transported through the maternal-fetal barrier.

The maternal phenotypic inheritance may hide risks for the newborn, too. Antibody mediated enhancement results in dengue shock syndrome in the first 8 month of age of the baby.

A series of pathologic maternal antibodies may elicit neonatal illnesses upon birth usually recovering during the first months of the life of the offspring. Certain antibodies, however, may impair the fetal or neonatal tissues or organs resulting prolonged recovery or initiating prolonged pathological processes of the children.

The importance of maternal anti-idiotypic antibodies are believed to prime the fetal immune system with epitopes of etiologic agents infected the mother during her whole life before pregnancy and delivery.

The chemotherapeutical and biological substances used for the therapy of the mother will be transcytosed into the fetal body during the last two trimesters of pregnancy. The long series of the therapeutic monoclonal antibodies and conjugates has not been tested systematically yet. The available data are summarised in this chapter.

The innate immunity plays an important role in fetal defence. The concentration of interferon is relative high in the placenta. This is probably one reason, why the therapeutic interferon treatment of the mother does not impair the fetal development.

Managing pregnancy in inflammatory rheumatological diseases

Historically, pregnancy in women with many inflammatory rheumatic diseases was not considered safe and was discouraged. Combined care allows these pregnancies to be managed optimally, with the majority of outcomes being favorable. Disease activity at the time of conception and anti-phospholipid antibodies are responsible for most complications. Disease flares, pre-eclampsia, and thrombosis are the main maternal complications, whereas fetal loss and intrauterine growth restriction are the main fetal complications. Antirheumatic drugs used during pregnancy and lactation to control disease activity are corticosteroids, hydroxychloroquine, sulphasalzine, and azathioprine. Vaginal delivery is possible in most circumstances, with cesarean section being reserved for complications.

Rheumatic diseases and pregnancy

PURPOSE OF REVIEW

This review discusses how inflammatory rheumatic diseases [rheumatoid arthritis, ankylosing spondylitis, systemic lupus erythematosus (SLE)] of the mother can influence the course of pregnancy and the development of the fetus. Antirheumatic drug therapy of the mother and strategies to prevent fetal complications namely in SLE must be considered with care.

RECENT FINDINGS

The current literature is presented discussing hypotheses about the immunologic mechanisms leading to amelioration or exacerbation of the rheumatic symptoms in rheumatoid arthritis and ankylosing spondylitis during pregnancy. In SLE, several recent studies have been published concerning fetal complications in the antiphospholipid syndrome and in Ro/SSA-positive and La/SSB-positive mothers and how to diagnose, treat, or prevent these.

SUMMARY

Today, women with inflammatory rheumatic diseases are normally fertile and can be encouraged to become pregnant, when there is a stable and quiescent phase of the disease. This is in particular important for patients with SLE, although pregnancy outcome in SLE has improved over the last decades. Pregnancy in SLE is still a high-risk period during the disease course with the highest risk in women with active lupus nephritis. In contrast, women with rheumatoid arthritis develop amelioration of the rheumatic symptoms during the course of pregnancy in most cases; female ankylosing spondylitis patients are likely to show unaltered or aggravated symptoms of back pain and impaired function.