Anti‐citrullinated glucose‐6‐phosphate isomerase peptide antibodies in patients with rheumatoid arthritis are associated with HLA‐DRB1 shared epitope alleles and disease activity

To identify and characterize anti‐citrullinated glucose‐6‐phosphate isomerase (GPI) peptide antibodies in patients with rheumatoid arthritis (RA). Nine GPI arginine‐bearing peptides in human GPI protein were selected and cyclic citrullinated GPI peptides (CCG‐1–9) were constructed. Samples were obtained from RA (n = 208), systemic lupus erythematosus (SLE) (n = 101), Sjögren's syndrome (SS; n = 101) and healthy controls (n = 174). Antibodies against CCG‐1–9 were measured, and anti‐citrullinated α‐enolase‐1 (CEP‐1), ‐cyclic citrullinated peptides (CCP) and ‐GPI proteins antibodies were also examined. Patients with RA were genotyped for HLA‐DRB1. The numbers of shared epitope (SE) alleles were counted and compared with those of the autoantibodies. Rabbit GPI was citrullinated with rabbit peptidylarginine deiminase and immunoblot analysis of RA sera performed. The levels of autoantibodies were compared before and after treatment with TNF antagonists in 58 RA patients. Anti‐CCG‐2, ‐4 and ‐7 antibodies were detected in 25·5, 33·2 and 37·0% patients with RA, respectively, and these antibodies were very specific for RA (specificity, 98·1–99·7%). Altogether, 44·2, 86·1 and 13·9% of RA sera were positive for anti‐CEP‐1, ‐CCP and ‐GPI protein antibodies, respectively. Anti‐CCG‐2, ‐4 and ‐7 antibodies were correlated with anti‐CCP and anti‐CEP‐1 antibodies and with the presence of HLA‐DRB1 SE alleles. Citrullinated GPI protein was detected using RA sera. Treatment with tumour necrosis factor antagonists reduced significantly the levels of anti‐CCG‐2 and ‐7 but not of anti‐CEP‐1 antibodies. This is the first report documenting the presence of anti‐CCG antibodies in RA. Anti‐CCG‐2 and ‐7 antibodies could be considered as markers for the diagnosis of RA and its disease activity.     

Fine specificity of anti‐citrullinated peptide antibodies discloses a heterogeneous antibody population in rheumatoid arthritis

Anti‐citrullinated peptide antibodies (ACPA) are highly specific for rheumatoid arthritis (RA). However, the predominant B cell epitopes have not yet been defined. The aim of this study was to examine the reactivity of ACPA against different peptides derived from citrullinated proteins and to investigate whether or not these antibodies constitute a homogeneous population. For this purpose, sera from patients with RA (n = 141), systemic lupus erythematosus (SLE) (n = 60), Sjögren's syndrome (SS) (n = 54) and healthy controls (n = 100) were tested for their reactivity against six citrullinated peptides derived from peptidyl arginine deiminase (PAD), vimentin (vim), alpha‐enolase (enol), fibrin, type II collagen (col‐II) and filaggrin, respectively. A non‐citrullinated control peptide derived from PAD was used as control (ctrlPAD^621–40). Antibody reactivity against each individual peptide was evaluated by enzyme‐linked immunosorbent assay (ELISA). Specificity and cross‐reactivity of ACPA were tested by using two prototype sera with homologous and cross‐inhibition assays. Specificity of ACPA from two prototype sera was confirmed by purification of anti‐peptide antibodies and homologous‐inhibition experiments. We found that sera from patients with RA reacted diversely with the six citrullinated peptides. More specifically, PAD^211–30 displayed 29·08% sensitivity, vim^60–75 29·08%, enol^5–21 37·59%, fibrin^617–31 31·21%, col‐II^358–75 29·97% and filaggrin^306–24 28·37%, while control ctrlPAD^621–40 showed no reactivity. All reactive peptides were found to be highly specific for RA. A notable cross‐reaction (>70%) was found mainly between filaggrin and the majority of anti‐citrullinated peptide antibodies. We concluded that ACPA in RA constitute a heterogeneous population with limited cross‐reactivity and without a predominant epitope.     

Immunoglobulin (Ig)M antibodies against oxidized cardiolipin but not native cardiolipin are novel biomarkers in haemodialysis patients,associated negatively with mortality

The risk of premature death is high in haemodialysis (HD) patients. Antibodies against cardiolipin (anti‐CL) are thrombogenic in diseases such as systemic lupus erythematosus (SLE). CL is easily oxidized (Ox) and plays a role in apoptosis. In this work we studied immunoglobulin (Ig)M anti‐CL and anti‐OxCL in HD‐patients. We conducted an observational study with a prospective follow‐up examining the relationship between anti‐CL, anti‐OxCL and mortality risk in a well‐characterized cohort of 221 prevalent HD patients [56% men, median age 66 (interquartile range 51–74) years, vintage time 29 (15–58) months] with a mean follow‐up period of 41 (20–48 months). According to the receiver operator characteristic (ROC) analysis, anti‐OxCL [area under the curve (AUC) 0·62, P < 0·01], but not anti‐CL (AUC 0·52, P = 0·2), is associated with mortality. In crude and adjusted Cox analysis, every log increase in anti‐OxCL inversely predicted all‐cause [adjusted hazard ratios (HR) 0·62 (0·43–0·89)] and CVD‐related [adjusted HR 0·56 (0·32–0·98)] mortality. Patients with anti‐OxCL levels below median also had increased all‐cause and cardiovascular disease (CVD)‐related mortality. Although anti‐OxCL and anti‐phosphorylcholine (PC) were related positively to each other (ρ = 0·57, P < 0·01), patients with one or two of these autoantibody levels below the median were associated with an incrementally increased death risk. Anti‐OxCL were co‐factor β2‐GPI‐independent; anti‐CL from patients with anti‐phospholipid antibody syndrome were β2‐GPI‐dependent, while sera from HD‐patients less so. Sera from healthy donors was not β2‐GPI‐dependent. Anti‐OxCL IgM is β2‐glycoprotein 1 (GPI)‐independent and a novel biomarker; low levels are associated with death among HD patients (and high levels with decreased risk). Combination with anti‐PC increases this association. Putative therapeutic implications warrant further investigation.     

Antibodies to age‐β2glycoprotein I in patients with anti‐phospholipid antibody syndrome

Anti‐phospholipid antibody syndrome (APS) is a systemic autoimmune disease characterized clinically by arterial and/or venous thromboses, recurrent abortions or fetal loss and serologically by the presence of ‘anti‐phospholipid antibodies’ (aPL). The main target antigen of the antibodies is β₂glycoprotein I (β₂GPI). Post‐translational oxidative modifications of the protein have been widely described. In this study we aimed to analyse sera reactivity to glucose‐modified β₂GPI (G‐β₂GPI). Sera collected from 43 patients with APS [15 primary APS (PAPS) and 28 APS associated with systemic lupus erythematosus (SLE) (SAPS)], 30 with SLE, 30 with rheumatoid arthritis (RA) and 40 healthy subjects were analysed by an enzyme‐linked immunosorbent assay (ELISA) using a G‐β₂GPI. Nine of 15 consecutive PAPS out‐patients (60%) and 16 of 28 SAPS (57.1%) showed serum antibodies [immunoglobulin (Ig)G class] against G‐β₂GPI (anti‐G‐β₂GPI) by ELISA. The occurrence of anti‐G‐β₂GPI was significantly higher in APS patients compared to patients suffering from SLE. No RA patients or control healthy subjects resulted positive for anti‐G‐β₂GPI. Of note, aG‐β₂GPI prompted to identify some APS patients (four PAPS and seven SAPS), who were negative in the classical anti‐β₂GPI test. Moreover, in APS patients, anti‐G‐β₂GPI titre was associated significantly with venous thrombosis and seizure in APS patients. This study demonstrates that G‐β₂GPI is a target antigen of humoral immune response in patients with APS, suggesting that β₂GPI glycation products may contain additional epitopes for anti‐β₂GPI reactivity. Searching for these antibodies may be useful for evaluating the risk of clinical manifestations.     

Comparative analysis of autoantibodies targeting peptidylarginine deiminase type 4, mutated citrullinated vimentin and cyclic citrullinated peptides in rheumatoid arthritis: associations with cytokine profiles,clinical and genetic features

Antibodies against cyclic citrullinated peptides (anti‐CCP) are widely used for diagnosis of rheumatoid arthritis (RA). We performed a comparative analysis of antibodies targeting the citrullinating enzyme peptidylarginine deiminase type 4 (anti‐PAD4) and mutated citrullinated vimentin (anti‐MCV) with anti‐CCP autoantibodies in RA patients and examined their relationships with clinical parameters, cytokine profiles and the PADI4 gene. Autoantibodies were examined by enzyme‐linked immunosorbent assay (ELISA) in sera of 170 RA patients and 103 controls. Cytokine profiles were measured using a multiplex system. PADI4 polymorphisms (89G > A, 90T > C and 92G > C) were genotyped by polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP). Anti‐PAD4, anti‐MCV and anti‐CCP autoantibodies were detected in 24, 61 and 74% of RA patients, respectively. Positive correlations were observed between anti‐PAD4 and disease duration; anti‐CCP and erythrocyte sedimentation rate (ESR); anti‐MCV and ESR and C‐reactive protein. Anti‐MCV antibodies were associated with high disease activity score 28 (DAS‐28) in early RA. Concentrations of T helper type 1 (Th1) [tumour necrosis factor (TNF)‐α, interleukin (IL)‐12, IL‐2, IL‐1β], Th2 (IL‐4, IL‐6, IL‐10, IL‐13) and Th17 (IL‐17) cytokines were higher in RA than in controls. Th2 and, to a lesser extent, Th1‐related cytokines, showed positive correlations with anti‐MCV and anti‐CCP. The GTG haplotype in PADI4 was associated with anti‐CCP and anti‐MCV, but not anti‐PAD4 antibodies. In conclusion, anti‐PAD4 antibodies are detected mainly in established RA, which is in contrast to the early detection of antibodies against citrullinated peptide/proteins (ACPAs). Among autoantibodies, anti‐MCV appear to perform better as markers of disease activity. Furthermore, anti‐CCP and anti‐MCV are associated genetically with the citrullinating enzyme PAD4 and are related strongly to Th1 and Th2 cytokines, suggesting a feed‐forward loop between cytokines and ACPA production.     

Immunoglobulin A anti‐phospholipid antibodies in Swedish cases of systemic lupus erythematosus: associations with disease phenotypes,vascular events and damage accrual

Immunoglobulin (Ig) G‐ and IgM‐class anti‐cardiolipin antibodies (aCL) and lupus anti‐coagulant (LA) are included in the 1997 update of the American College of Rheumatology (ACR‐97) systemic lupus erythematosus (SLE) criteria. Despite limited evidence, IgA‐aCL and IgA anti‐β₂‐glycoprotein‐I (anti‐β₂GPI) were included in the 2012 Systemic Lupus International Collaborating Clinics criteria. The present study aimed to evaluate IgG‐/IgA‐/IgM‐aCL and anti‐β₂GPI occurrence in relation to disease phenotype, smoking habits, pharmacotherapy, anti‐phospholipid syndrome (APS) and organ damage among 526 Swedish SLE patients meeting ACR‐97. Patients with rheumatoid arthritis (n = 100), primary Sjögren’s syndrome (n = 50) and blood donors (n = 507) served as controls. Anti‐phospholipid antibodies (aPL) were analysed by fluoroenzyme‐immunoassays detecting aCL/anti‐β₂GPI. Seventy‐six (14%) SLE cases fulfilled the Sydney APS‐criteria, and ≥ 1 aCL/anti‐β₂GPI isotype (IgG/IgA/IgM) occurred in 138 SLE patients (26%). Forty‐five (9%) of the SLE cases had IgA‐aCL, 20 of whom (4%) lacked IgG‐/IgM‐aCL. Seventy‐four (14%) tested positive for IgA anti‐β₂GPI, 34 (6%) being seronegative regarding IgG/IgM anti‐β₂GPI. Six (1%) had APS manifestations but were seropositive regarding IgA‐aCL and/or IgA anti‐β₂GPI in the absence of IgG/IgM‐aPL and LA. Positive LA and IgG‐aPL tests were associated with most APS‐related events and organ damage. Exclusive IgA anti‐β₂GPI occurrence associated inversely with Caucasian ethnicity [odds ratio (OR) = 0·21, 95% confidence interval (CI) = 0·06–0·72) and photosensitivity (OR = 0·19, 95% CI = 0·05–0·72). Nephritis, smoking, LA‐positivity and statin/corticosteroid‐medication associated strongly with organ damage, whereas hydroxychloroquine‐medication was protective. In conclusion, IgA‐aPL is not rare in SLE (16%) and IgA‐aPL analysis may have additional value among SLE cases with suspected APS testing negative for other isotypes of aPL and LA.     

Relationship between natural and infection‐induced antibodies in systemic autoimmune diseases (SAD): SLE,SSc and RA

Infection or vaccine‐induced T cell‐dependent immune response and the subsequent high‐affinity neutralizing antibody production have been extensively studied, while the connection between natural autoantibodies (nAAbs) and disease‐specific antibodies has not been thoroughly investigated. Our goal was to find the relationship between immunoglobulin (Ig)M and IgG isotype nAAbs and infection or vaccine‐induced and disease‐related autoantibody levels in systemic autoimmune diseases (SAD). A previously described indirect enzyme‐linked immunosorbent assay (ELISA) test was used for detection of IgM/IgG nAAbs against citrate synthase (anti‐CS) and F4 fragment (anti‐F4) of DNA topoisomerase I in 374 SAD samples, with a special focus on systemic lupus erythematosus (SLE) (n = 92), rheumatoid arthritis (n = 73) and systemic sclerosis (n = 157) disease groups. Anti‐measles IgG and anti‐dsDNA IgG/IgM autoantibodies were measured using commercial and in‐house indirect ELISA tests. In all SAD groups the anti‐measles IgG‐seropositive cases showed significantly higher anti‐CS IgG titers (P = 0·011). In anti‐dsDNA IgG‐positive SLE patients, we detected significantly higher levels of anti‐CS and anti‐F4 IgG nAAbs (P = 0·001 and < 0·001, respectively). Additionally, we found increased levels of IgM isotypes of anti‐CS and anti‐F4 nAAbs in anti‐dsDNA IgM‐positive SLE patients (P = 0·002 and 0·016, respectively). The association between IgG isotypes of pathogen‐ or autoimmune disease‐related antibodies and the IgG nAAbs may underscore the immune response‐inducible nature of the diseases investigated. The relationship between protective anti‐dsDNA IgM and the IgM isotype of anti‐F4 and anti‐CS may provide immunoserological evidence for the beneficial roles of nAAbs in SLE patients.     

Anti‐Citrullinated Peptide Antibodies in Sudanese Patients with Leishmania donovani Infection Exhibit Reactivity not Dependent on Citrullination

African patients with Leishmania donovani infections have signs of strong systemic inflammation and high levels of circulating immune complexes (IC) and rheumatoid factor (RF), all serologic markers of rheumatic disease. As inflammation in general is associated with citrullination, we sought to investigate ACPA responses in Sudanese Leishmania patients. Serum samples were collected from Sudanese patients with visceral leishmaniasis (VL) and post‐kala‐azar dermal leishmaniasis (PKDL) as well as from ACPA‐positive Sudanese rheumatoid arthritis patients and compared to healthy Sudanese controls. Levels of circulating C1q‐binding IC and anticyclic citrullinated peptide 2(CCP2) were investigated using ELISA, and RF was measured with nephelometry. C1q adsorption was carried out to investigate anti‐CCP2 content in IC. Citrulline specificity was evaluated with control plates with cyclic arginine‐containing control peptides. Leishmania‐infected patients had elevated levels of RF and circulating IC but also a significant increase in anti‐CCP2 (12%) as compared to healthy controls. Anti‐CCP2‐positive Leishmania patients displayed lower anti‐CCP2 levels than Sudanese patients with rheumatoid arthritis (RA), and anti‐CCP2 levels in Leishmania patients showed a continuum not resembling the dichotomous pattern seen in patients with RA. Whereas the anti‐CCP reactivity of Sudanese RA sera was strictly citrulline dependent, anti‐CCP2‐positive Leishmania sera reacted equally well with ELISA plates containing arginine control peptides. There was a strong correlation between anti‐CCP2 and circulating IC among the Leishmania patients, but IC depletion only marginally diminished anti‐CCP2 levels. Our findings stress the importance to interpret a positive CCP test carefully when evaluated in non‐rheumatic conditions associated with macrophage activation.     

Increased prevalence of autoimmunity in Turner syndrome – influence of age

Individuals with Turner syndrome (TS) are prone to develop autoimmune conditions such as coeliac disease (CD), thyroiditis and type 1 diabetes (T1DM). The objective of the present study was to examine TS of various karyotypes for autoantibodies and corresponding diseases. This was investigated in a prospective cross‐sectional study of Danish TS patients (n = 107, median age 36·7 years, range: 6–60 years). A medical history was recorded and a blood sample was analysed for autoantibodies against gliadin, transglutaminase, adrenal cortex, intrinsic factor, anti‐thyroid peroxidase (anti‐TPO) and glutamic‐acid‐decarboxylase 65 (GAD‐65). Autoantibodies were present in 58% (n = 61) of all patients, whereof 18% (11) had autoantibodies targeting more than one organ. Patients with autoantibodies were significantly older than those without (P = 0·001). Anti‐TPO was present in 45% (48) of patients, of whom 33% (16) were hypothyroid. Overall, 18% (19) presented with CD autoantibodies, of whom 26% (five) had CD. Anti‐TPO and CD autoantibodies co‐existed in 9% (10). Immunoglobulin A deficiency was found in 3% (three) of patients, who all had CD autoantibodies without disease. Among four patients with anti‐GAD‐65 none had T1DM, but two were classified as having T2DM. One patient had adrenocortical autoantibodies but not adrenal failure. Autoantibodies against intrinsic factor were absent. Anti‐GAD‐65 was increased in isochromosomal karyotypes (3/23 versus 1/84, P = 0·008) with no other association found between autoantibodies and karyotype. In conclusion, TS girls and women face a high prevalence of autoimmunity and associated disease with a preponderance towards hypothyroidism and CD. Thus, health care providers dealing with this patient group should be observant and test liberally for these conditions even before clinical symptoms emerge.     

Anti‐C1q autoantibodies are linked to autoimmune thyroid disorders in pregnant women

Anti‐C1q antibodies (anti‐C1q) have been implicated in the pathogenesis of autoimmune diseases, including autoimmune thyroid disorders (AITD). The aim of this study was to evaluate the association between anti‐C1q and thyroid function in pregnancy‐associated AITD. In 96 pregnant women screened positive for AITD (thyroid dysfunction and/or antibodies against thyroperoxidase – TPOAb), anti‐C1q were measured during the 9‐11th gestational week and after delivery (median 16 months after delivery), and compared to the corresponding serum levels of thyroid hormones. As controls, 80 healthy pregnant women, 72 non‐pregnant AITD patients and 72 blood donors were included. In the non‐pregnant AITD group, two serum samples ≥ 6 months apart were analysed. Compared to blood donors, anti‐C1q levels were substantially higher in all pregnant women analysed. In pregnancy, anti‐C1q levels were higher in the TPOAb‐positive women than in controls (37 versus 17·5%, P < 0·0001). Anti‐C1q‐positive pregnant women screened positive for AITD had higher thyroid‐stimulating hormone (TSH) levels than anti‐C1q‐negative women (2·41 versus 1·94 mU/l, P = 0·01), and TSH correlated positively with anti‐C1q (r = 0·226, P = 0·045) in the TPOAb‐positive women. After delivery, serum levels of anti‐C1q decreased in the positively screened TPOAb‐negative women (8·8 versus 5·9 U/l, P = 0·002), but not in the TPOAb‐positive ones, and they no longer correlated with TSH. Anti‐C1q antibody levels increase during pregnancy in general and even more in the context of AITD, where they correlate with thyroid stimulating hormone levels.     

Immunoglobulin (Ig)G1 and IgG4 anti‐cyclic citrullinated peptide (CCP) associate with shared epitope,whereas IgG2 anti‐CCP associates with smoking in patients with recent‐onset rheumatoid arthritis (the Swedish TIRA project)

Given the possible importance of anti‐citrullinated peptide/protein antibodies (ACPA) for initiation and progression of rheumatoid arthritis (RA), extended knowledge about the different isotypes and subclasses is important. In the present study, we analysed the immunoglobulin (Ig)G subclasses regarding reactivity against cyclic citrullinated peptides (anti‐CCP) among 504 clinically well‐characterized patients with recent‐onset RA in relation to smoking habits, shared epitope (SE) status and IgA and pan‐IgG anti‐CCP antibodies. All patients, regardless of pan‐IgG anti‐CCP status, were analysed for IgG1–4 CCP reactivity. Sixty‐nine per cent were positive in any IgG anti‐CCP subclass, and of these 67% tested positive regarding IgG1, 35% IgG2, 32% IgG3, and 59% IgG4 anti‐CCP. Among ever‐smokers the percentages of IgG2 anti‐CCP (P = 0·01) and IgA anti‐CCP (P = 0·002)‐positive cases were significantly higher compared to never‐smokers. A positive IgG anti‐CCP subclass ‐negative cases. Combining SE and smoking data revealed that IgG1 and IgG4 anti‐CCP were the IgG anti‐CCP isotypes associated with expression of SE, although the lower number of patients positive for IgG2 or IgG3 anti‐CCP could, however, have influenced the results. High levels of IgG2 anti‐CCP were shown to correlate with expression of the ‘non‐SE’ allele human leucocyte antigen (HLA)‐DRB1*15. In conclusion, in this study we describe different risk factor characteristics across the IgG anti‐CCP subclasses, where IgG2 appears similar to IgA anti‐CCP regarding the predominant association with smoking, while IgG1 and IgG4 related more distinctly to the carriage of SE genes.     

Associations of B cell‐activating factor (BAFF) and anti‐BAFF autoantibodies with disease activity in multi‐ethnic Asian systemic lupus erythematosus patients in Singapore

To measure the levels of B cell‐activating factor (BAFF) and endogenous anti‐BAFF autoantibodies in a cohort of multi‐ethnic Asian systemic lupus erythematosus (SLE) patients in Singapore, to determine their correlation with disease activity. Serum samples from 121 SLE patients and 24 age‐ and sex‐matched healthy controls were assayed for BAFF and anti‐BAFF immunoglobulin (Ig)G antibody levels by enzyme‐linked immunosorbent assay (ELISA). The lowest reliable detection limit for anti‐BAFF‐IgG antibody levels was defined as 2 standard deviations (s.d.) from blank. Correlation of serum BAFF and anti‐BAFF IgG levels with disease activity [scored by SLE Activity Measure revised (SLAM‐R)], and disease manifestations were determined in these 121 patients. SLE patients had elevated BAFF levels compared to controls; mean 820 ± 40 pg/ml and 152 pg ± 45/ml, respectively [mean ± standard error of the mean (s.e.m.), P < 0·01], which were correlated positively with anti‐dsDNA antibody levels (r = 0·253, P < 0·03), and SLAM‐R scores (r = 0·627, P < 0·01). In addition, SLE patients had significantly higher levels of anti‐BAFF IgG, which were correlated negatively with disease activity (r = –0·436, P < 0·01), levels of anti‐dsDNA antibody (r = –0·347, P < 0·02) and BAFF (r = –0·459, P < 0·01). The majority of patients in this multi‐ethnic Asian SLE cohort had elevated levels of BAFF and anti‐BAFF antibodies. Anti‐BAFF autoantibody levels correlated negatively with clinical disease activity, anti‐dsDNA and BAFF levels, suggesting that they may be disease‐modifying. Our results provide further information about the complexity of BAFF pathophysiology in different SLE disease populations and phenotypes, and suggest that studies of the influence of anti‐cytokine antibodies in different SLE populations will be required when selecting patients for trials using targeted anti‐cytokine therapies.     

Increased CTLA‐4+ T cells may contribute to impaired T helper type 1 immune responses in patients with chronic obstructive pulmonary disease

Impaired T helper type 1 (Th1) function is implicated in the susceptibility of patients with chronic obstructive pulmonary disease (COPD) to respiratory infections, which are common causes of acute exacerbations of COPD (AECOPD). To understand the underlying mechanisms, we assessed regulatory T (Treg) cells and the expression of an inhibitory T‐cell receptor, cytotoxic T‐lymphocyte‐associated antigen 4 (CTLA‐4). Cryopreserved peripheral blood mononuclear cells (PBMC) from patients with AECOPD (n = 17), patients with stable COPD (sCOPD; n = 24) and age‐matched healthy non‐smoking controls (n = 26) were cultured for 24 hr with brefeldin‐A or monensin to detect intracellular or surface CTLA‐4 (respectively) by flow cytometry. T cells in PBMC from AECOPD (n = 9), sCOPD (n = 14) and controls (n = 12) were stimulated with anti‐CD3 with and without anti‐CTLA‐4 blocking antibodies and cytokines were quantified by ELISA. Frequencies of circulating T cells expressing intracellular CTLA‐4 were higher in sCOPD (P = 0·01), whereas patients with AECOPD had more T cells expressing surface CTLA‐4 than healthy controls (P = 0·03). Increased frequencies of surface CTLA‐4⁺ CD4⁺ T cells and CTLA‐4⁺ Treg cells paralleled increases in plasma soluble tumour necrosis factor receptor‐1 levels (r = 0·32, P = 0·01 and r = 0·29, P = 0·02, respectively) in all subjects. Interferon‐γ responses to anti‐CD3 stimulation were inversely proportional to frequencies of CD4⁺ T cells expressing intracellular CTLA‐4 (r = −0·43, P = 0·01). Moreover, CTLA‐4 blockade increased the induction of interferon‐γ, tumour necrosis factor‐α and interleukin‐6 in PBMC stimulated with anti‐CD3. Overall, chronic inflammation may expand sub‐populations of T cells expressing CTLA‐4 in COPD patients and therefore impair T‐cell function. CTLA‐4 blockade may restore Th1 function in patients with COPD and so aid the clearance of bacterial pathogens responsible for AECOPD.     

Anti‐centrosome antibodies: Prevalence and disease association in Chinese population

Anti‐centrosome antibodies are rare findings with undefined clinical significance in clinical research. We aimed at investigating the prevalence and clinical significance of anti‐centrosome antibodies in Chinese population. Testing results of total of 281,230 ANA‐positive sera were retrospectively obtained from West China Hospital Sichuan University in China between 2008 and 2017. We retrospectively collected and analysed the clinical and laboratory data of the patients with positive anti‐centrosome antibody. Of the 356 453 patients tested, 281 230 patients had positive antinuclear antibodies (ANAs, 78.9%), but only 78 patients with positive anti‐centrosome antibodies (0.022%), of which 74.4% are females. Diagnoses were established in 69 of 78 patients: 37 cases were autoimmune diseases, mainly including undifferentiated connective tissue diseases (UCTD, 9/37), rheumatoid arthritis (RA, 6/37), Sjögren's syndrome (SS, 5/37) and primary biliary cirrhosis (PBC, 5/37), and the remaining were other autoimmune conditions. The most frequent clinical symptoms of the anti–centrosome‐positive patients were arthralgia and eyes and mouth drying. Additionally, 86.7% of anti‐centrosome antibodies were not associated with other ANA profiles; however, when associated, the most frequent ANA was anti‐U1RNP. Anti‐centrosome antibodies are featured by a low prevalence and female gender predominance. They are correlated with some specific diseases, both autoimmune diseases, especially UCTD, RA, SS and PBC, and non‐autoimmune diseases, such as infection and cancer, which suggests that they might be potential supporting serological markers of these diseases.     

The Investigation on the Value of Repeat and Combination Test of ACA and Anti‐β2‐GPI Antibody in Women with Recurrent Spontaneous Abortion

Problem In order to investigate the value of anticardiolipin antibodies (ACA) and anti‐β₂‐GPI antibodies detection in screening autoimmune type recurrent spontaneous abortion and its clinic application in antiphospholipid syndrome diagnosis, we adopt repeat combined ACA and anti‐β₂‐GPI antibodies detection in this study. Method of study Sera were collected from patients and work‐up was done for detection of ACA and anti‐β₂‐GPI antibodies by enzyme‐linked immunosorbent assay (ELISA). The work‐up was done for detection of antibodies once in every 6 weeks for 14 times consecutively. Results The repeated and combined detection of ACA and anti‐β₂‐GPI antibodies detection could raise the positivity rate up to 21.8% (P < 0.05) in comparison with positive for ACA alone (14.1%), positive for anti‐β₂‐GPI alone (3.1%), and concurrently positive for both ACA and anti‐β₂‐GPI antibodies (4.6%). In 91 confirmed positive antiphospholipid antibodies (APA) patients, with more frequent screening for ACA and anti‐β₂‐GPI antibodies, more patients with APA were found. The positive rate of five and more screenings was over 81.32%, which was statistically significant (P < 0.05), in comparison with that of four or less screenings (68.13%). Conclusion Our data implied that it would be appropriate to take over five or more screenings of combined ACA and anti‐β₂‐GPI antibodies detection in suspect patients to facilitate the positive diagnostic rate for autoimmune type RSA.     

Cross-reaction between antibodies to the major epitope of Ro60 kD autoantigen and a homologous peptide of Coxsackie virus 2B protein

Coxsackie virus RNA has recently been detected in biopsy specimens of minor salivary glands from patients with primary Sjögren's Syndrome (pSS). A peptide derived from Coxsackie virus 2B protein (pepCoxs) presents 87% sequence homology with the 222–229 region of the major linear B‐cell epitope of Ro60 kD autoantigen (pep216–232). Synthetic peptides corresponding to pep216–232: ²¹⁶KALSVETEKLLKYLEAV²³² and pepCoxs: ³¹MVTSTITEKL LKNLVKI⁴⁷, were prepared. Sera from 42 patients with pSS and 43 patients with systemic lupus erythematosus (SLE) as well as sera from 27 healthy individuals (normal controls) and sera from 30 patients with rheumatoid arthritis (disease controls) were tested against the two homologous peptides. Twenty‐five percent of SLE sera and 33·3% of pSS sera reacted against pep216–232, whereas 28% of SLE sera and 37% of pSS sera recognized the pepCoxs. The sera reacting with pep216–232 were apparently the same as those reacting with pepCoxs. Normal sera and disease control sera presented only a limited reactivity against both peptides (ranging from 3·7% to 10%). Both peptides reacted more prominently with anti‐Ro/La (+) sera from pSS patients. Thus, pep216–232 was recognized by 17% of the anti‐Ro (+) sera and by 42% of the anti‐Ro/La (+) sera, whereas pepCoxs was recognized by 28·5% and 38% of the a‐Ro(+) and a‐Ro/La(+) sera, respectively. Purified anti‐pep216–232 antibodies readily reacted with both peptides while inhibition experiments revealed the specificity of this reaction. These results suggest a possible cross‐reaction between antibodies to the major linear B‐cell epitope of Ro60 kD autoantigen and the homologous pepCoxs in pSS patients. This cross‐reaction might potentially play a role in autoantibody formation and the perpetuation of the autoimmune response against Ro/SSA and La/SSB.     

Rheumatoid arthritis is caused by a Proteus urinary tract infection

Genetic, molecular and biological studies indicate that rheumatoid arthritis (RA), a severe arthritic disorder affecting approximately 1% of the population in developed countries, is caused by an upper urinary tract infection by the microbe, Proteus mirabilis. Elevated levels of specific antibodies against Proteus bacteria have been reported from 16 different countries. The pathogenetic mechanism involves six stages triggered by cross‐reactive autoantibodies evoked by Proteus infection. The causative amino acid sequences of Proteus namely, ESRRAL and IRRET, contain arginine doublets which can be acted upon by peptidyl arginine deiminase thereby explaining the early appearance of anti‐citrullinated protein antibodies in patients with RA. Consequently, RA patients should be treated early with anti‐Proteus antibiotics as well as biological agents to avoid irreversible joint damages.     

Calreticulin is a B cell molecular target in some gastrointestinal malignancies

Calreticulin, upon translocation to the cell surface, plays a critical role in the recognition of tumour cells and in experimentally induced cellular anti‐tumour immunity. However, less is known about anti‐calreticulin antibodies and their role in malignancies. Using enzyme‐linked immunosorbent assay (ELISA), we found immunoglobulin (Ig)A and/or IgG anti‐calreticulin antibodies in sera of approximately 63% of patients with hepatocellular carcinoma (HCC), 57% of patients with colorectal adenocarcinoma (CRA) and 47% of patients with pancreatic adenocarcinoma (PACA), while healthy controls, patients with viral hepatitis C and with chronic pancreatitis reached only 2%, 20% and 31% seropositivity, respectively. We found significantly elevated mean levels of IgA anti‐calreticulin antibodies (P < 0·001) in patients with HCC (78·7 ± 52·3 AU, mean ± standard deviation), PACA (66·5 ± 30·9 AU) and CRA (61·8 ± 25·8 AU) when compared to healthy controls (41·4 ± 19·2 AU). Significantly elevated mean levels of IgG anti‐calreticulin antibodies (P < 0·001) were detected in patients with HCC (121·9 ± 94·2 AU), gall bladder adenocarcinoma (118·4 ± 80·0 AU) and PACA (88·7 ± 55·6 AU) when compared to healthy controls (56·7 ± 22·9 AU). Pepscan analysis revealed a large number of antigenic epitopes of calreticulin recognized by both IgA and IgG antibodies of patients with HCC and PACA, indicating robust systemic immune response. Moreover, significantly elevated levels of antibodies against peptide KGEWKPRQIDNP (P < 0·001) in these patients, tested by ELISA, confirmed the distinct character of antibody reactivity against calreticulin. The high occurrence and specificity of serum anti‐calreticulin autoantibodies in the majority of patients with some gastrointestinal malignancies provide the evidence for their possible clinical relevance.     

Clinical significance of autoantibodies recognizing Sjögren's syndrome A (SSA), SSB, calpastatin and alpha-fodrin in primary Sjögren's syndrome

The aim of our study was (i) to compare the clinical and biological characteristics of 148 (137 women, 11 men) primary Sjögren's syndrome (pSS) patients at diagnosis as a function of their sex and (ii) to assess the prognostic value of anti‐calpastatin and anti‐alpha‐fodrin autoantibodies. In addition, the presence of anti‐nuclear antibodies (ANA), anti‐52‐ and 60‐kDa Sjögren's syndrome A (SSA), anti‐Sjögren's syndrome B (SSB), anti‐cyclic citrullinated peptide (CCP) antibodies and rheumatoid factors (RF) of IgA, IgG and IgM isotypes was sought in sera collected at pSS onset. Raynaud's syndrome, significantly more frequent in women, was the only systemic manifestation of pSS whose frequency differed significantly as a function of the patient's sex (P = 0·02). ANA (P = 0·001) and anti‐60‐kDa SSA autoantibodies (P = 0·03) were significantly more common in women, while men never synthesized detectable levels of anti‐SSB, anti‐calpastatin or IgG anti‐alpha‐fodrin autoantibodies. In addition, anti‐CCP autoantibodies were found in low percentages of pSS patients (4% F/18% M). The absence of autoantibodies does not exclude the diagnosis of pSS in men that will be based mainly on the anatomopathological findings of a minor salivary gland biopsy. Positivity of anti‐60‐kDa SSA, anti‐SSB, anti‐calpastatin, IgA and IgG anti‐alpha‐fodrin antibodies is not associated with pSS clinical and biological severity.     

Racially restricted contribution of immunoglobulin Fcγ and Fcγ receptor genotypes to humoral immunity to human epidermal growth factor receptor 2 in breast cancer

Tumour‐associated antigen human epidermal growth factor receptor 2 (HER2) is over‐expressed in 25–30% of breast cancer patients and is associated with poor prognosis. Naturally occurring anti‐HER2 antibody responses have been described in patients with HER2 over‐expressing tumours. There is significant interindividual variability in antibody responsiveness, but the host genetic factors responsible for this variability are poorly understood. The aim of the present investigation was to determine whether immunoglobulin genetic markers [GM (genetic determinants of γ chains)] and Fcγ receptor (FcγR) alleles contribute to the magnitude of natural antibody responsiveness to HER2 in patients with breast cancer. A total of 855 breast cancer patients from Japan and Brazil were genotyped for several GM and FcγR alleles. They were also characterized for immunoglobulin (Ig)G antibodies to HER2. In white subjects (n = 263), GM 23‐carriers had higher levels of anti‐HER2 antibodies than non‐carriers of this allele (p = 0·004). At the GM 5/21 locus, the homozygotes for the GM 5 allele had higher levels of anti‐HER2 antibodies than the other two genotypes (P = 0·0067). In black subjects (n = 42), FcγRIIa‐histidine/histidine homozygotes and FcγRIIIa‐phenylalanine/valine heterozygotes were associated with high antibody responses (P = 0·0071 and 0·0275, respectively). FcγR genotypes in white subjects and GM genotypes in black subjects were not associated with anti‐HER2 antibody responses. No significant associations were found in other study groups. These racially restricted contributions of GM and FcγR genotypes to humoral immunity to HER2 have potential implications for immunotherapy of breast cancer.