Agalactosyl IgG in pristane-induced arthritis. Pregnancy affects the incidence and severity of arthritis and the glycosylation status of IgG

The history of IgG glycosylation and where we are now

IgG glycosylation is currently at the forefront of both immunology and glycobiology, likely due in part to the widespread and growing use of antibodies as drugs. For over four decades, it has been recognized that the conserved N-linked glycan on asparagine 297 found within the second Ig domain of the heavy chain (CH2) that helps to comprise Fc region of IgG plays a special role in IgG structure and function. Changes in galactosylation, fucosylation and sialylation are now well-established factors, which drive differential IgG function, ranging from inhibitory/anti-inflammatory to activating complement and promoting antibody-dependent cellular cytotoxicity. Thus, if we are to truly understand how to design and deploy antibody-based drugs with maximal efficacy and evaluate proper vaccine responses from a protective and functional perspective, a deep understanding of IgG glycosylation is essential. This article is intended to provide a comprehensive review of the IgG glycosylation field and the impact glycans have on IgG function, beginning with the earliest findings over 40 years ago, in order to provide a robust foundation for moving forward.

Glycosylation of plasma IgG in colorectal cancer prognosis

In this study we demonstrate the potential value of Immunoglobulin G (IgG) glycosylation as a novel prognostic biomarker of colorectal cancer (CRC). We analysed plasma IgG glycans in 1229 CRC patients and correlated with survival outcomes. We assessed the predictive value of clinical algorithms and compared this to algorithms that also included glycan predictors. Decreased galactosylation, decreased sialylation (of fucosylated IgG glycan structures) and increased bisecting GlcNAc in IgG glycan structures were strongly associated with all-cause (q < 0.01) and CRC mortality (q = 0.04 for galactosylation and sialylation). Clinical algorithms showed good prediction of all-cause and CRC mortality (Harrell's C: 0.73, 0.77; AUC: 0.75, 0.79, IDI: 0.02, 0.04 respectively). The inclusion of IgG glycan data did not lead to any statistically significant improvements overall, but it improved the prediction over clinical models for stage 4 patients with the shortest follow-up time until death, with the median gain in the test AUC of 0.08. These glycan differences are consistent with significantly increased IgG pro-inflammatory activity being associated with poorer CRC prognosis, especially in late stage CRC. In the absence of validated biomarkers to improve upon prognostic information from existing clinicopathological factors, the potential of these novel IgG glycan biomarkers merits further investigation.

Pristane-induced arthritis loci interact with the Slc11a1 gene to determine susceptibility in mice selected for high inflammation

AIRmax (maximal inflammation) and AIRmin (minimal inflammation) mice show distinct susceptibilities to pristane-induced arthritis (PIA). The Slc11a1 gene, which regulates macrophage and neutrophil activity, is involved in this infirmity. AIRmax^SS mice homozygous for the non-functional Slc11a1 S (gly169asp) allele obtained by genotype-assisted crosses from AIRmax and AIRmin mice are more susceptible than mice homozygous for the Slc11a1 resistant (R) allele. The present work sought to identify the quantitative trait loci (QTL) regulating PIA and to examine the interactions of these QTL with Slc11a1 alleles in modulating PIA. Mice were given two ip injections of 0.5 mL pristane at 60 day intervals, and the incidence and severity of PIA was scored up to 160 days. Genome-wide linkage studies were performed to search for arthritis QTL in an F2 (AIRmax × AIRmin, n = 290) population. Significant arthritis QTL (LODscore>4) were detected on chromosomes 5 and 8, and suggestive QTL on chromosomes 7, 17 and 19. Global gene expression analyses performed on Affymetrix mouse 1.0 ST bioarrays (27k genes) using RNA from arthritic or control mice paws showed 419 differentially expressed genes between AIRmax and AIRmin mice and demonstrated significantly (P<0.001) over-represented genes related to inflammatory responses and chemotaxis. Up-regulation of the chemokine genes Cxcl1, Cxcl9, Cxcl5, Cxcl13 on chromosome 5 was higher in AIRmax^SS than in the other lines. Macrophage scavenger receptor 1 and hemeoxigenase (decycling) 1 genes on chromosome 8 were also expressed at higher levels in AIRmax^SS mice. Our results show that the gene expression profiles of the two arthritis QTL (on chromosomes 5 and 8) correlate with Slc11a1 alleles, resulting in enhanced AIRmax^SS mice susceptibility to PIA.

N-glycomic biomarkers of biological aging and longevity: a link with inflammaging

Glycosylation is a frequent co/post-translational modification of proteins which modulates a variety of biological functions. The analysis of N-glycome, i.e. the sugar chains N-linked to asparagine, identified new candidate biomarkers of aging such as N-glycans devoid of galactose residues on their branches, in a variety of human and experimental model systems, such as healthy old people, centenarians and their offspring and caloric restricted mice. These agalactosylated biantennary structures mainly decorate Asn297 of Fc portion of IgG (IgG-G0), and are present also in patients affected by progeroid syndromes and a variety of autoimmune/inflammatory diseases. IgG-G0 exert a pro-inflammatory effect through different mechanisms, including the lectin pathway of complement, binding to Fcγ receptors and formation of autoantibody aggregates. The age-related accumulation of IgG-G0 can contribute to inflammaging, the low-grade pro-inflammatory status that characterizes elderly, by creating a vicious loop in which inflammation is responsible for the production of aberrantly glycosylated IgG which, in turn, would activate the immune system, exacerbating inflammation. Moreover, recent data suggest that the N-glycomic shift observed in aging could be related not only to inflammation but also to alteration of important metabolic pathways. Thus, altered N-glycans are both powerful markers of aging and possible contributors to its pathogenesis.

Rheumatoid arthritis and pregnancy: evolution of disease activity and pathophysiological considerations for drug use

It has long been known that pregnancy and childbirth have a profound effect on the disease activity of rheumatic diseases. For clinicians, the management of patients with RA wishing to become pregnant involves the challenge of keeping disease activity under control and adequately adapting drug therapy during pregnancy and post-partum. This article aims to summarize the current evidence on the evolution of RA disease activity during and after pregnancy and the use of anti-rheumatic drugs around this period. Of recent interest is the potential use of anti-TNF compounds in the preconception period and during pregnancy. Accumulating experience with anti-TNF therapy in other immune-mediated inflammatory diseases, such as Crohn's disease, provides useful insights for the use of TNF blockade in pregnant women with RA, or RA patients wishing to become pregnant.

Glycan profiling of anti-citrullinated protein antibodies isolated from human serum and synovial fluid

OBJECTIVE

Anti-citrullinated protein antibodies (ACPA) exhibit unique specificity for rheumatoid arthritis. However, it is incompletely understood whether and how ACPA contribute to disease pathogenesis. The Fc part of human IgG carries 2 N-linked glycan moieties that are crucial for the structural stability of the antibody and that modulate both its binding affinity to Fcgamma receptors and its ability to activate complement. We undertook this study to analyze Fc glycosylation of IgG1 ACPA in serum and synovial fluid (SF) in order to further characterize the immune response to citrullinated antigens.

METHODS

ACPA were isolated by affinity purification using cyclic citrullinated peptides as antigen. IgG1 Fc glycosylation was analyzed by mass spectrometry. ACPA IgG1 glycan profiles were compared with glycan profiles of total serum IgG1 obtained from 85 well-characterized patients. Glycan profiles of paired SF and serum samples were available from 11 additional patients.

RESULTS

Compared with the pool of serum IgG1, ACPA IgG1 lacked terminal sialic acid residues. In SF, ACPA were highly agalactosylated and lacked sialic acid residues, a feature that was not detected for total SF IgG1. Moreover, differential ACPA glycan profiles were detected in rheumatoid factor (RF)-positive and RF-negative patients.

CONCLUSION

ACPA IgG1 exhibit a specific Fc-linked glycan profile that is distinct from that of total serum IgG1. Moreover, Fc glycosylation of ACPA differs markedly between SF and serum. Since Fc glycosylation directly affects the recruitment of Fc-mediated effector mechanisms, these data could further our understanding of the contribution of ACPA to disease pathogenesis.

Impact of glycans on T-cell tolerance to glycosylated self-antigens

There is now substantial evidence that antigen post-translational modifications are recognized by T cells, and alterations in epitope modification has been linked to a number of autoimmune diseases. An estimated one third of the MHC ligands contain post-translational modification of epitopes. A common post-translational modification of proteins is glycosylation and it is predicted on theoretical grounds that approximately 1-5% of MHC ligands may bear a glycan. From numerous studies over the past 15 years it is clear that glycans can influence T cell responses either by contribution to the structure of the epitope or by influencing the profile of peptide epitopes presented by APCs. The influence of glycans on antigen processing and T cell recognition has particular relevance to the induction of tolerance to self-antigens. Here we discuss the potential impact of glycans on the profile of self-epitopes presented by APCs and the consequence of changes in glycosylation to generate neo self-epitopes resulting in the loss of tolerance and the development of autoimmune diseases. With the recent developments in profiling T cell epitopes, and with strategies for modulating glycosylation in vivo, it is now feasible to directly examine the global influence of glycans on self-tolerance and autoimmunity.

Slc11a1 (formerly NRAMP1) gene modulates both acute inflammatory reactions and pristane-induced arthritis in mice

Mice selected for the maximum acute inflammatory reaction (AIRmax) are highly susceptible to pristane-induced arthritis (PIA), whereas mice selected for the minimum response (AIRmin) are resistant. These lines show distinct patterns of leukocyte infiltration and R and S allele frequency disequilibrium of the solute carrier family 11a member 1 (Slc11a1) gene. In order to study the interactions of the Slc11a1 R and S alleles with the inflammation modulating Quantitative Trait Loci (QTL) during PIA development, homozygous AIRmax(RR), AIRmax(SS), AIRmin(RR) and AIRmin(SS) lines were produced by genotype-assisted breedings. These mice received two intraperitoneal injections of 0.5 ml pristane at 60-day intervals, and the subsequent development of arthritis was assessed for 210 days. Cytokine-secreting cell profiles were investigated using enzyme-linked immunospot. Arthritis incidence in AIRmax(RR) mice reached 29%, whereas PIA incidence in AIRmax(SS) mice was 70% by day 180. AIRmin(RR) mice were resistant, whereas 13.3% of AIRmin(SS) mice became arthritic. The presence of the defective S allele also increased arthritis severity, although acute inflammation was higher in mice bearing the R allele. A predominant Th0/Th2-type response in Slc11a1(SS) mice was observed. These results indicate that Slc11a1 is a strong candidate for the QTL modulating acute inflammation and for PIA.

Reactivity of T cells from women with antibodies to the human platelet antigen (HPA)-1a to peptides encompassing the HPA-1 polymorphism

The human platelet antigen-1a (HPA-1a) is the most common alloantigenic target in fetal and neonatal alloimmune thrombocytopenia (NAIT). Treatment currently depends on the outcome in previous pregnancies. HPA-1 specific T cell responses were determined in 14 HPA-1a alloimmunized women during or after pregnancies affected by NAIT. Peripheral blood mononuclear cells were incubated with peptides encompassing the Leu33Pro polymorphism (residues 20-39 and 24-45 in both Leu33 (HPA-1a) and Pro33 (HPA-1b) forms) or control recall antigens in the presence of autologous sera and T cell proliferation was measured by (3)H-thymidine incorporation. Control antenatal and postpartum sera suppressed T cell proliferation and use of such sera was avoided. Most patients (86%) responded to the HPA-1a peptides with 64% also having weaker T cell proliferation to the HPA-1b peptides; 14% had no activity towards any peptide despite responding to control antigens. Administration of IVIG during pregnancy appeared to reduce T cell reactivity to HPA-1 peptides. Postnatal anti-HPA-1a T cell responses from women who had a severe history of NAIT (an intracranial haemorrhage in a previous fetus) were greater than those from women with a mild history. This assay may have the potential to predict disease severity if performed prior to or early in pregnancy.

Increased levels of galactose-deficient IgG in sera of HIV-1-infected individuals

BACKGROUND

The IgG from sera of patients with chronic inflammatory diseases of autoimmune character or some chronic microbial infections is frequently deficient in galactose on N-linked glycans. However, this phenomenon has not been investigated at length in human viral infections.

OBJECTIVES

To evaluate the glycosylation of serum IgG in HIV-1-positive patients.

METHODS

Psathyrella velutina lectin was used in enzyme-linked immunosorbent and Western blot assays to determine glycosylation. In addition, gas-liquid chromatography and mass spectrometry were utilized to confirm the galactose deficiency observed in the lectin-binding assays.

RESULTS

HIV-1-infected individuals had significantly higher levels of galactose-deficient IgG than healthy controls. In fact, the galactose deficiency of the N-linked glycans observed in other diseases was even more profound in HIV-1 infection. This deficiency was primarily restricted to IgG when total serum glycoproteins were evaluated and IgG1 was the subclass most affected in all patients. Also, a significant increase in lectin binding was observed on IgG2 and IgG4 from HIV-1-positive females compared with HIV-1-negative females.

CONCLUSIONS

Identification of deficient galactosylation of serum IgG from HIV-1-infected patients extended the spectrum of diseases in which this phenomenon has been observed. In addition, the results suggest yet another aspect of immune dysfunction as a result of HIV-1 infection.

Galactosylation of serum IgG and autoantibodies in murine models of autoimmune haemolytic anaemia

A number of systemic autoimmune diseases are associated with increased levels of the agalactosyl (G0) IgG isoforms that lack a terminal galactose from the CH2 domain oligosaccharide. The current aim was to determine whether the galactosylation of serum IgG is also reduced in a classic antibody-mediated, organ-specific autoimmune condition, and whether the pathogenic autoantibodies are preferentially G0. In two murine forms of autoimmune haemolytic anaemia (AIHA), sera and autoantibodies eluted from erythrocytes were obtained, and the levels of G0 measured using a lectin-binding assay. Serum IgG galactosylation was unaffected following the induction of AIHA in CBA/Igb mice by immunization with rat erythrocytes, but in all animals with the disease the IgG autoantibodies generated were more G0 than the sera. The anti-rat erythrocyte antibodies were similar to the autoantibodies in being preferentially G0, and when CBA/Igb mice were immunized with canine erythrocytes as a control foreign antigen, there was again a bias towards the production of G0 IgG antibodies. In NZB mice with chronic, spontaneous AIHA, the concentration and galactosylation of both serum IgG and autoantibodies were lower than in the induced model, and the ratio of G0 IgG in the serum and erythrocyte eluates varied markedly between different individuals. Our interpretation of these results is that changes in serum IgG or autoantibody galactosylation are not consistent in different models of AIHA, and that production of low galactosyl antibodies can be a feature of a normal immune response.

The role of glycosylation in autoimmune disease

Oligosaccharide structures play a key role in the antigenicity of a number of clinically important antigens such as blood group determinants. Interest in glycobiology has increased dramatically amongst immunologists during the last few years due to the fact that oligosaccharides also play a central role in adhesion and homing events during inflammatory processes (1), comprise powerful xenotransplantation antigens (2), and may provide targets for tumor immunotherapy (3). Additionally, alterations in glycosylation are now known to occur in a number of autoimmune diseases. This review will first discuss some general aspects of protein glycosylation and then explore some of the autoimmune diseases in which the role of glycosylation has been examined.

Changes in agalactosyl IgG levels correlate with radiological progression in early rheumatoid arthritis

Immunoglobulin G-lacking galactose (Gal[0]) appears to be helpful in differential diagnosis of early synovitis, and correlates with disease activity in rheumatoid arthritis (RA). Its utility for RA monitoring and prognosis has been evaluated in the present study. Forty-eight patients with early RA were observed for 3 years. Hand radiographs were assessed according to Larsen and results were expressed as damage score (DS) and progression of damage score (PDS). Gal[0], DS, and PDS were evaluated at the onset of the study and after 1 and 3 years. The average values of Gal[0] in RA patients at the onset of the observation were significantly higher as compared to healthy controls (0.43 +/- 0.22 vs. -0.03 +/- 0.09, P < 0.05). The findings of Gal[0] after a 3-year follow-up were also higher as compared to healthy controls (0.37 +/- 0.21 vs. -0.03 +/- 0.09, P < 0.05). Radiological progression (PDS > 15) was observed in 16 patients. This group was characterized by a constantly high level of Gal[0]. The level of Gal[0] in patients without or with moderate radiological progression (PDS < 15) was significantly lower at the onset of the study and remained low during the observation. The relationship between Gal[0] and radiological progression was shown. The data thus far obtained suggest that Gal[0] may serve as an indicator for the disease course in patients with RA. Secondly, we cannot exclude the possibility that the constantly elevated level of Gal[0] causes erosions.

Agalactosyl IgG and beta-1,4-galactosyltransferase gene expression in rheumatoid arthritis patients and in the arthritis-prone MRL lpr/lpr mouse

Reduced galactosylation of immunoglobulin G (IgG) is well documented in rheumatoid arthritis (RA), but the reason for this defect is still unknown. There is some evidence supporting a defect in the biosynthetic pathway, and a reduction in the level of beta-1,4-galactosyltransferase (beta-1,4-GalTase) enzyme activity. Since glycosyltransferases are, in general, regulated at the level of transcription, we have measured the level of beta-1,4-GalTase gene expression in B cells from patients with RA and normal control individuals. We found no significant difference in mRNA levels for the transferase in these two groups (P > 0.7). MRL/Mp-lpr/lpr (MRL-lpr) mice develop a spontaneous arthritis with increased levels of agalactosyl IgG (G0). In spite of a significant reduction in the level of beta-1,4-GalTase mRNA in total spleen lymphocytes from MRL-lpr mice compared with the congenic MRL/Mp-(+/+) (MRL-(+/+) mice and with CBA/Ca mice, we found comparable levels of the beta-1,4-GalTase mRNA in purified B cells from both spleen and lymph nodes of the three strains. Amongst the lymphoid compartments examined, the spleen and peripheral blood were found to be the major contributors of G0 in MRL-lpr mice. These data indicate that in neither human RA, nor in an animal model of this disease, is reduced IgG galactosylation caused by impaired expression of the beta-1,4-GalTase gene in B lymphocytes. Furthermore, splenic B cells, which have normal levels of beta-1,4-GalTase mRNA, appear to be a major source of G0 in MRL-lpr mice.

The Serum Level of Agalactosyl IgG in Rheumatoid Arthritis Patients Treated with Methotrexate

To verify the hypothesis that methotrexate may affect the serum level of agalactosyl IgG (IgG[0]) we followed the changes in IgG galactosylation patterns in a cohort of rheumatoid arthritis patients treated with either methotrexate (MTX) or nonsteroidal antiinflammatory drugs (NSAID).

The average values of IgG[0] in RA patients at the beginning of the observation were significantly higher as compared to healthy controls (0.45 ± 0.39 vs. −0.03 ± 0.09, p<0.05). The findings of IgG[0] after one-year follow-up were also higher as compared to healthy controls (0.38 ± 0.39 vs. −0.03 ± 0.09, p<0.05).

We did not notice any statistically significant difference in IgG[0] between MTX and NSAID treated patients at the beginning of the study (0.49 ± 0.42 vs. 0.42 ± 0.38, NS). However, during one-year MTX treatment IgG[0] significantly dropped (0.49 ± 0.42 vs. 0.25 ± 0.24, p<0.01). We did not establish any fluctuation in IgG[0] in the group of patients treated with NSAID (0.42 ± 0.38 vs. 0.46 ± 0.45, NS).

The data thus far obtained suggest that IgG[0] may serve as an indicator for the disease course in patients with RA. Secondly, the clinical improvement and IgG[0] decrease after methotrexate implies, that the immunoregulatory abnormality in RA may be susceptible to correction by immunotherapy.

Agalactosyl IgG and materno-fetal transmission of autoimmune neonatal lupus

Neither the incidence nor the severity of neonatal autoimmune disease correlates with maternal or neonatal autoantibody titres. However, there is now evidence that the agalactosyl [Gal(0)] fractions of autoantibodies are the most pathogenic. We found that systemic lupus erythematosus (SLE) mothers whose infants developed congenital heart block (CHB) had higher %Gal(0) at the end of pregnancy than did mothers of unaffected infants (P < 0.05) or control mothers (P < 0.01). Similarly, affected infants had higher %Gal(0) than control infants (P < 0.01). Then we studied the Gal(0) content of the anti-Ro and we found that it was higher in affected neonates than in unaffected neonates (P < 0.05), though there was no difference between the corresponding groups of mothers by this criterion. We propose that agalactosyl IgG may have a regulatory or effector role and that the risk of neonates developing maternal autoantibody-mediated disorders may be related to the quantity of agalacotsyl autoantibody present at birth, rather than to its absolute titre.

Neonatal myasthenia gravis and the role of agalactosyl IgG

Neonatal autoimmune diseases are thought to be due to the transfer of maternal autoantibodies. However, there is a puzzling lack of correlation between maternal autoantibody titres and disease in the neonate. So far, no factor reliably predictive of neonatal disease has been found. Agalactosyl IgG is a variable feature of normal IgG. Preliminary studies indicated that the percentage of agalactosyl IgG is lower in the serum of normal neonates, than in the serum of the mother at delivery. Since raised % agalactosyl IgG is often associated with autoimmune disease we sought to determine whether this relationship holds true in a neonatal autoimmune disease. We measured the % agalactosyl IgG in paired maternal-cord sera from patients with myasthenia gravis, some of whom had offspring with neonatal myasthenia gravis. We found that the percentage of agalactosyl IgG was significantly higher in affected than in unaffected neonates. Moreover % agalactosyl IgG was higher in sera of affected neonates than in serum from their mothers, while unaffected infants of mothers with myasthenia had %Gal(0) lower than their mothers, mimicking the normal situation. This suggests that in affected neonates a high proportion of the IgG is synthesised by the baby itself rather than derived from the mother. This agrees with previous evidence based on the presence of idiotypes not found in the mother which implied that the neonates with neonatal myasthenia gravis produce their own autoantibodies.

Immunotoxicity of silicone: implications of oxidant balance towards adjuvant activity

A variety of mechanisms can be proposed to explain the potential effects of silicone and silicone by-products on the immune response. In this paper, we discuss information on the chemistry of silicon and silicone gels/elastomers, and the manufacture of silicone breast implants as they pertain to the bioreactivity of silicone. Moreover, with reference to silicone-mediated human adjuvant disease, an overview of experimental adjuvant-induced arthritis is presented; comparisons with graft-versus-host disease and chemically induced autoimmunity then follow. Particular attention is paid to similarities in the characteristics of silicone and classic lipid adjuvants. For example, macrophage activation is presumed to be a central event in silicone-induced autoimmunity. Since those genes uniquely expressed in macrophages activated by plastic adherence are similar to those induced by lipopolysaccharide, adherence to silicone rubber may initiate an inflammatory response by the same mechanism. Macrophage effects would also include the erosion of implants through the generation of oxidants and localized pH changes. The degradation products of silicone are also implicated in the adjuvant effects of silicone implants. There is evidence to suggest that oxidants produced by inflammatory cells preferentially inactivate CD8+ suppressor T cells. This could then lead to an inflammatory state, perhaps through oxidant-induced transcription factors such as NF-kB, resulting in a long-term pro-oxidant imbalance that manifests itself as a breakdown in immunological self-tolerance. The authors hypothesize that autoreactivity following oxidant stress evolved to enhance inflammatory repair mechanisms after tissue, cell or molecular damage by oxidants.

Reduced galactosyltransferase mRNA levels are associated with the agalactosyl IgG found in arthritis-prone MRL-lpr/lpr strain mice

MRL-lpr/lpr strain mice have defectively glycosylated IgG. This may be related to the rheumatoid arthritis (RA)-like disease that occurs in these mice, because a similar glycosylation defect is seen in human subjects with RA. Whilst it is known that this defect is associated with reduced activity of the beta-1,4-galactosyltransferase (beta-1,4-GalTase) enzyme, the cause of this reduced activity is at present unknown. We have therefore examined the molecular genetics of beta-1,4-GalTase in MRL-lpr/lpr mice. Using 10 different restriction endonucleases we found no evidence for a polymorphic variant of the gene in glycosylation-defective mice. However, the level of mRNA for beta-1,4-GalTase was lowest in the MRL-lpr/lpr mice, the strain with the most poorly galactosylated IgG of the four strains examined. Thus, the reduced level of IgG oligosaccharide galactosylation found in MRL-lpr/lpr strain mice appears to be related to either an altered transcriptional level of, or altered mRNA stability for, beta-1,4-GalTase in lymphocytes from these mice.

Evaluation of a model for post-partum arthritis and the role of oestrogen in prevention of MRL-lpr associated rheumatic conditions

Sixty-eight percent of female MRL-lpr mice developed a post-partum exacerbation of their mild spontaneous arthritis within 30 days of parturition. The flare became evident between 5 and 15 days after delivery. Histologically it was characterized by a significant increase of subsynovial inflammation and synovial hyperplasia without changes in the level of cartilage and bone erosion. Immunohistologically, marked subsynovial and frequent synovial staining of MHC class II bearing cells was noted, along with the sporadic presence of CD3, CD4, and CD43 receptor-bearing cells in the subsynovium. Injection of physiological levels (0.08 mg/kg) of estradiol on days 2, 3, 9, 15 and 20 post-partum delayed and reduced the flare to 23% of the animals. Administration of pharmacological amounts (0.4 mg/kg per day for 2 weeks following Freund's complete adjuvant injection) prevented adjuvant-enhanced arthritis, reducing the incidence from 67% to the baseline 21% level. Deleterious changes in the underlying systemic lupus erythematosus (SLE), as demonstrated by proteinuria and mortality rate increases, were elicited only by the employed pharmacological amounts of estradiol. These results indicate that the MRL-lpr mice might serve as a model for post-partum flare of arthritis in SLE and rheumatoid arthritis by providing an approach to study the complexity of the effects of pregnancy on autoimmune diseases, and to obtain further evidence for the involvement of oestrogen in arthritis.

A longitudinal study of per cent agalactosyl IgG in tuberculosis patients receiving chemotherapy, with or without immunotherapy

An increased percentage of circulating IgG molecules that lack galactose from the oligosaccharides on the CH2 domain correlates with disease severity in tuberculosis, rheumatoid arthritis and Crohn's disease. We have recently observed that a single injection of 10(9) autoclaved Mycobacterium vaccae given to tuberculosis patients 7 days after the initiation of chemotherapy causes accelerated clinical improvement, and clearance of bacilli from the sputum. We now show that this immunotherapy also causes rapid loss of agalactosyl IgG, detectable within 14-21 days, whereas chemotherapy alone causes agalactosyl IgG to rise further for up to 2 months. There is simultaneous inhibition of the antibody response to lipoarabinomannan, and transient enhancement of the tuberculin skin-test response. These findings are compatible with a shift from antibody production towards increased cell-mediated immunity. The ideal treatment for tuberculosis would supplement a truncated course of chemotherapy with an immunotherapeutic preparation able to down-regulate the Koch phenomenon and replace it with an efficiently bactericidal mechanism. We tentatively postulate that a fall in per cent agalactosyl IgG [%Gal(0)] in tuberculosis patients may be a marker of such a change.

IgG glycosylation in autoimmune-prone strains of mice

The relationship between increased levels of IgG oligosaccharide chains lacking galactose (G0) and the development of rheumatoid arthritis is unclear. In order to further our understanding of the observed correlation between raised serum G0 and arthritis, we have studied G0 levels in arthritis-prone and non-susceptible (i.e. non-arthritis-prone) mice and the effects on G0 of mycobacterial antigens, which have been postulated to play a role in the early events leading to the development of arthritis. We have shown that different age-matched mouse strains have characteristic 'resting' levels of G0 which (in six out of seven strains of mice) increase with age. We have also shown that these increases can be enhanced by immunization of arthritis-prone strains of mice with an adjuvant containing mycobacteria (Freund's complete adjuvant (FCA)), suggesting that deflects in the ability to regulate these G0 changes may be related to susceptibility to arthritis.

Comparison between the protective effects of mycobacterial 65-kD heat shock protein and ovomucoid in pristane-induced arthritis: relationship with agalactosyl IgG

The IgG of patients with rheumatoid arthritis and mice with pristane induced arthritis (PIA) tends to lack the terminal galactose normally on the conserved N-acetylglucosamine linked beta 1-2 to mannose in IgG. The terminal N-acetylglucosamine (GlcNAc) residues of oligosaccharides on agalactosyl IgG may be an important component of the action of these glycoforms. Here, administration of ovomucoid, a glycoprotein rich in terminal GlcNAc, before pristane injection was found to reduce the incidence of PIA. This observation is the second report of an intraperitoneally administered antigen that reduces the incidence of PIA, mycobacterial 65-kD heat shock protein (hsp65) being the first. The suppressive effect of ovomucoid was not transferred from protected to naive recipients by spleen cells at the dose tested. By contrast, transfer of spleen cells from hsp65-protected mice to naive recipients conferred protection and this protection may be antibody-mediated. It is considered that ovomucoid and hsp65 protect against the development of PIA by different mechanisms.

Prevention of pristane-induced arthritis by the oral administration of type II collagen

This is the first demonstration of a role for type II collagen in pristane-induced arthritis. Pretreatment with soluble type II collagen either lowers or raises the subsequent incidence and severity of pristane-induced arthritis. These effects are dependent upon both the dose and route of administration of the soluble type II collagen. Increasing doses of orally administered type II collagen lowered both the incidence and severity of pristane-induced arthritis. Conversely, increasing doses of intraperitoneally administered type II collagen increased both the incidence and severity of arthritis. This exacerbation of pristane-induced arthritis was accompanied by elevated B- and T-cell responses to type II collagen. These findings highlight the importance of the site at which antigen is encountered in influencing subsequent immune responses and extend the observations of the use of orally administered antigens to ameliorate experimental autoimmunity.