High diagnostic value of anticalpastatin autoantibodies in rheumatoid arthritis detected by ELISA using human erythrocyte calpastatin as antigen

OBJECTIVE: To develop a quantitative method of measuring autoantibodies against human calpastatin in rheumatoid arthritis (RA) and to determine their diagnostic value compared with other autoimmune and articular diseases. METHODS: We performed a highly sensitive ELISA for IgG and IgM anticalpastatin autoantibodies in human sera using human erythrocyte calpastatin as an antigen. Samples were diluted 1:2000 for the measurement of IgG and 1:400 for IgM. RESULTS: IgG anticalpastatin antibodies were found in the sera of 48 of 58 patients (82.8%) with RA. In contrast, IgG anticalpastatin antibodies were found in the sera of only 2 of 11 (8.3%) patients with osteoarthritis (OA). Compared to sera from patients with other autoimmune diseases, anticalpastatin antibody sensitivity for RA was better than that of systemic lupus erythematosus (5.6%), systemic sclerosis (0%), mixed connective tissue disease (0%), and Sj?gren's syndrome (20%). IgG anticalpastatin antibodies also showed high specificity (96.1%) for RA. Almost 90% of patients with RA were positive for IgG or IgM anticalpastatin antibodies. CONCLUSION: We have developed a simple, sensitive, specific, and quantitative ELISA for anticalpastatin antibodies that may have a high diagnostic value for RA.     

IgG, IgA, IgM antibodies to a viral citrullinated peptide in patients affected by rheumatoid arthritis, chronic arthritides and connective tissue disorders

OBJECTIVES: Anti-citrullinated protein/peptide antibodies (ACPA), a family of antibodies with overlapping specificities, represent a specific marker of rheumatoid arthritis (RA). The aim of the present study is to investigate the prevalence and clinical significance of IgG, IgA and IgM ACPA by a newly described assay employing a viral citrullinated peptide (VCP). METHODS: IgG, IgA and IgM anti-VCP antibodies have been measured in sera from 146 patients affected by RA and 404 controls, including 204 chronic arthritides, 111 connective tissue disorders and 89 healthy subjects. The affinity of the different isotypes for VCP was analysed by liquid phase inhibition assays. RESULTS: Among RA patients, 40 were single positive for IgG anti-VCP, five for IgA and 11 for IgM. Ten patients were double positive for IgG and IgA, four for IgG and IgM, six for IgA and IgM. In 15 RA patients IgG, IgA and IgM anti-VCP antibodies were detected. No correlation could be found between the isotype and the clinical manifestations or duration of the disease. IgA anti-VCP were strongly associated with RA, whereas IgM anti-VCP were detected also in a low percentage of systemic lupus erythematosus, psoriatic arthritis and mixed cryoglobulinaemia (MC) patients. IgG anti-VCP displayed a higher affinity for the antigen than IgA or IgM. CONCLUSIONS: These data show that anti-VCP of IgG and IgA isotype discriminate RA from other chronic arthritides and disease controls and suggest an independent production of each isotype.     

Anti-Human type II collagen CD19+ B cells are present in patients with rheumatoid arthritis and healthy individuals.

OBJECTIVE: To determine the frequency and repertoire of CD19+ B cells capable of producing antibodies reactive to type II collagen (CII) in synovial fluid (SF) and peripheral blood (PB) of patients with rheumatoid arthritis (RA) and PB of healthy control individuals. METHODS: CD19+ B cells were isolated and activated to secrete immunoglobulins (Ig) by CD4+ T cells. Frequencies of anti-CII B cells were determined by limiting dilution analysis. The isotype and cross-reactivity of the antibodies produced were determined by ELISA. RESULTS: SF and PB from 5 patients and PB from 4 healthy controls were analyzed. Anti-CII CD19+ B cells were identified in all samples tested. In the RA SF, the percentage of activated B cells reactive to human CII was significantly higher than in the PB of patients with RA (p < 0.05) or controls (p < 0.01). A majority of anti-human CII B cells from patients' SF secreted IgG isotype, whereas most anti-human CII B cells in PB of patients and controls secreted IgM. The anti-CII B cells, regardless of source, are usually reactive to both native and denatured human CII, to different types of human collagens, and to type II collagens from different species. CONCLUSION: Anti-CII CD19+ B cells responsive to activated helper T cells are present in both patients with RA and healthy individuals. However, these B cells, especially those secreting the IgG isotype, accumulate in the inflamed joints of RA patients.     

Raised serum IgG and IgA antibodies to mycobacterial antigens in rheumatoid arthritis.

Autoantigens cross reactive with mycobacteria are implicated in the pathogenesis of adjuvant arthritis in the rat, and there are reports of changes in the immune response to mycobacteria in human rheumatoid arthritis (RA). We have therefore examined the IgM, IgG, and IgA antibody levels to crude mycobacterial antigens and to two recombinant mycobacterial heat shock/stress proteins (65 kD and 71 kD) in sera from patients with RA, systemic lupus erythematosus (SLE), and Crohn's disease, and from healthy controls. IgA binding to the crude mycobacterial antigens was significantly raised in RA sera, though IgG and IgM binding tended to be lower than in controls. Both IgA and IgG binding to the heat shock proteins were significantly raised in the RA sera. Smaller significant rises in both classes were seen in sera from patients with SLE, and in the IgA class only to the 65 kD protein in Crohn's disease. The rises in IgG and IgA antibodies to the 65 kD protein in RA were significantly higher than in the other diseases, however. It is interesting that this protein is the one responsible for adjuvant arthritis in the rat.     

Anti-cyclic citrullinated peptide antibody isotypes in rheumatoid arthritis: association with disease duration, rheumatoid factor production and the presence of shared epitope

OBJECTIVE: Anti-cyclic citrullinated peptide (anti-CCP) antibodies of IgG isotype are specific diagnostic markers of rheumatoid arthritis (RA). Recent evidence also points to their direct involvement in the pathophysiology. Little information is available, however, regarding the isotype distribution of anti-CCP antibodies and the characteristics of IgA and IgM anti-CCP. METHODS: IgG, IgA and IgM anti-CCP2 and rheumatoid factor (RF) levels were measured in the sera of 119 RA patients and 118 controls, including patients with other rheumatic diseases and healthy subjects. We analyzed the diagnostic performance of IgA and IgM anti-CCP2 antibodies and their relationship with IgG anti-CCP2, RFs, disease duration and the presence of HLA-DRB1 shared epitope (SE) alleles. RESULTS: Patients with RA had significantly higher serum IgA and IgM anti-CCP2 antibody levels than healthy subjects and patients with other rheumatic diseases (p<0.0001). IgG, IgA and IgM anti-CCP2 antibodies were present in 74.8%, 52.9% and 44.5% of RA patients, and their diagnostic specificity was 95.8%, 95.8% and 91.6%, respectively. The presence of anti-CCP2 antibodies was significantly associated with SE alleles (p=0.03). The frequency of IgM anti-CCP2 positivity was lower in longstanding disease compared to early RA (p=0.03). CONCLUSION: IgA and IgM anti-CCP2 antibodies are present in RA patients, and they are similarly specific for RA as IgG anti-CCP2. The higher frequency of IgM anti-CCP2 antibodies in early RA suggests that they are mostly generated during the first phase of immune response; nonetheless, their production seems to be sustained in some patients. Further analysis of IgM and IgA anti-CCP2 antibodies may provide insights into the pathogenesis of RA.     

Plasma cell dyscrasia and peripheral neuropathy: identification of the myelin antigens that react with human paraproteins.

In some cases of polyneuropathy and plasma cell dyscrasia, the monclonal antibodies react with human peripheral nerve myelin. To identify the myelin antigens involved, we separated the proteins of human central and peripheral nerve myelin by polyacrylamide gel electrophoresis, transferred the proteins onto nitrocellulose sheets, and used an immunoenzymatic technique to detect the reactive antigens. Serum IgM but not IgG from three patients with neuropathy and complement-fixing anti-human myelin IgM paraproteins immunostained a protein of approximately 100,000 daltons in human peripheral nerve myelin and a protein or closely migrating proteins of similar size in human central nervous system myelin. In a fourth patient, both IgM and IgG immunostained the antigen. Immunostaining was specific for the paraprotein light chain type, and absorption of the patients' sera with human peripheral nerve myelin eliminated the reaction with the central nervous system proteins. No reaction was seen with rabbit peripheral nerve myelin or with membranes prepared from human myotubes, human T cells, or human fibroblasts. Control sera from six patients with neuropathy and IgM paraproteins that did not react with myelin, from four patients with IgM paraproteins but no neuropathy, and from three normal subjects did not immunostain myelin.     

Elevated levels of IgM and IgA antibodies to Proteus mirabilis and IgM antibodies to Escherichia coli are associated with early rheumatoid factor (RF)-positive rheumatoid arthritis

OBJECTIVE: Antibodies to Proteus mirabilis were previously detected in patients with established rheumatoid arthritis (RA). We examined the prevalence of antibodies to P. mirabilis and their associations with RA in early synovitis patients. METHODS: Two hundred and forty-six patients with inflammatory arthritis for less than 1 yr were prospectively evaluated for 1 yr. Of these patients, 30% had rheumatoid factor (RF)-positive RA, 16% RF-negative RA, 17% a spondyloarthropathy and 37% undifferentiated arthritis. Serum antibodies to P. mirabilis, Escherichia coli and other potentially arthritogenic organisms (Chlamydia, Salmonella, Shigella, Campylobacter, Yersinia and parvovirus B19) and for antibodies specific for immunoglobulin (Ig) G damaged with advanced glycation end-products (anti-IgG-AGE) were measured. RESULTS: IgM and IgA anti-Proteus antibodies were significantly higher in patients with RF-positive RA compared with all other patient groups (P < 0.0005 and P < 0.005). Anti-P. mirabilis IgG, and IgG, IgA, and IgM antibodies to other potentially arthritogenic pathogens did not differ in the patient groups. IgM antibodies to E. coli were elevated in RF-positive RA patients. Anti-P. mirabilis IgM and IgA results were not explained by false-positive reactions, because after absorption of RF there was no decrease in antibodies to Proteus in 10 of 12 patients. Proteus and E. coli antibodies were highest in patients positive for both RF and anti-IgG-AGE antibodies (P<0.001). Patients with erosions tended to have higher IgA anti-Proteus titres, but no association with the shared HLA epitope or treatment was detected. CONCLUSION: Anti-P. mirabilis IgM and IgA and anti-E. coli IgM antibody elevations are associated with early seropositive RA and the presence of anti-IgG-AGE antibodies. The role that P. mirabilis or E. coli plays in early RF-positive RA requires further investigation.     

The gut-joint axis: cross reactive food antibodies in rheumatoid arthritis

BACKGROUND AND AIMS: Patients with rheumatoid arthritis (RA) often feel there is an association between food intake and rheumatoid disease severity. To investigate a putative immunological link between gut immunity and RA, food antibodies were measured in serum and perfusion fluid from the jejunum of RA patients and healthy controls to determine the systemic and mucosal immune response. METHODS: IgG, IgA, and IgM antibodies to dietary antigens were measured in serum and jejunal perfusion fluid from 14 RA patients and 20 healthy subjects. The antigens originated from cow's milk (alpha-lactalbumin, beta-lactoglobulin, casein), cereals, hen's egg (ovalbumin), cod fish, and pork meat. RESULTS: In intestinal fluid of many RA patients, all three immunoglobulin classes showed increased food specific activities. Except for IgM activity against beta-lactoglobulin, all other IgM activities were significantly increased irrespective of the total IgM level. The RA associated serum IgM antibody responses were relatively much less pronounced. Compared with IgM, the intestinal IgA activities were less consistently raised, with no significant increase against gliadin and casein. Considerable cross reactivity of IgM and IgA antibodies was documented by absorption tests. Although intestinal IgG activity to food was quite low, it was nevertheless significantly increased against many antigens in RA patients. Three of the five RA patients treated with sulfasalazine for 16 weeks had initially raised levels of intestinal food antibodies; these became normalised after treatment, but clinical improvement was better reflected in a reduced erythrocyte sedimentation rate. CONCLUSIONS: The production of cross reactive antibodies is strikingly increased in the gut of many RA patients. Their food related problems might reflect an adverse additive effect of multiple modest hypersensitivity reactions mediated, for instance, by immune complexes promoting autoimmune reactions in the joints.     

Evidence for local synthesis of antibodies to denatured collagen in the synovium in rheumatoid arthritis

Synovial fluid samples from 36 patients with rheumatoid arthritis (RA) and 31 patients with other articular diseases (OAD) were examined for the presence of antibodies to denatured or native human type II collagen. Levels of IgG antibodies to denatured or native human type II collagen, rheumatoid factor, immunoglobulins, and total proteins were assessed in paired samples of serum and synovial fluid from 21 patients with RA and from 14 patients with OAD. Solid-phase radioimmunoassay showed that levels of antibodies to denatured collagen in synovial fluid were significantly higher in RA patients than in OAD patients (median 3,270, range 44-16,816 versus median 919, range 119-5,814; P less than 0.001). These antibody levels were higher in synovial fluid than in the serum of RA patients, but not in patients with OAD. Paired serum and synovial fluid samples showed no correlation between the level of antibodies to denatured collagen and levels of either IgG, IgA, IgM, or rheumatoid factor. Synovial fluid antibodies to native collagen were higher in RA patients. Antibodies to collagen may be synthesized preferentially in synovial tissues and, hence, participate in the perpetuation of RA.     

Anti-myeloperoxidase antibodies in patients with rheumatoid arthritis: prevalence, clinical correlates, and IgG subclass.

OBJECTIVES--To determine the prevalence and clinical associations of autoantibodies to myeloperoxidase (MPO) in an unselected series of well-characterised outpatients with rheumatoid arthritis (RA) and to compare the distribution of IgG subclasses of anti-MPO antibodies in these patients with that in patients with systemic vasculitis. PATIENTS AND METHODS--A study was made of 97 patients with RA, who have been seen regularly in this department for up to 20 years, and 29 patients with anti-neutrophil cytoplasmic antibody (ANCA) positive systemic vasculitis. Anti-MPO antibodies were detected using a direct-binding enzyme-linked immunosorbent assay (ELISA) with MPO from human granulocytes as antigen. The IgG subclass of anti-MPO antibodies was determined by ELISA using isotype specific monoclonal antibodies. RESULTS--Anti-MPO antibodies were detected in 12% of patients with RA. Six sera contained IgG anti-MPO antibodies only, 1 IgM only and 5 antibodies of both classes. In the patients with RA the predominant subclasses were IgG1 and IgG3: only 2 sera contained detectable IgG4 antibodies. This was in contrast to patients with vasculitis, in whom most sera contained IgG1, IgG3 and IgG4 anti-MPO antibodies. Anti-MPO antibodies in sera from both patient groups bound only to the native protein. None of the patients studied with RA had evidence of vasculitis affecting the nerves or kidney: three patients (1 positive for anti-MPO antibodies and 2 negative) had cutaneous vasculitis. In the patients with RA, positivity for anti-MPO antibodies was associated with nodules and number of active joints. Three patients with anti-MPO antibodies, and none without, had pulmonary fibrosis. CONCLUSIONS--Twelve per cent of a group of unselected outpatients with RA, but without evidence of major systemic vasculitis, had anti-MPO antibodies in their serum. Positivity for anti-MPO antibodies was more common in patients with nodular disease and lung involvement but not in patients with cutaneous vasculitis. IgG4 sub-class anti-MPO antibodies were present in 90% of sera from patients with ANCA-positive vasculitis and only 2/11 (18%) of anti-MPO antibody containing sera from patients with RA.     

Antibodies against native type II collagen do not precede the clinical onset of rheumatoid arthritis

Serum levels of IgG and IgM antibodies to native human type II collagen were determined in 22 pre-illness sera from subjects who developed seropositive rheumatoid arthritis (RA) 4 months to 5 years after sera were obtained, in 51 specimens from 35 healthy controls, and in 4-5 specimens from 58 patients with recent-onset RA. The antibody levels in all pre-illness serum specimens fell within the range seen for the healthy controls. Four RA patients had an IgG class antibody level and 4 had an IgM class antibody level that was above the highest level observed for controls, in at least 1 serum sample. No significant difference in the mean level of anticollagen antibodies was observed in the followup specimens from RA patients.     

Antinuclear antibodies following infliximab treatment in patients with rheumatoid arthritis or spondylarthropathy

OBJECTIVE: To investigate the effect of infliximab treatment on antinuclear antibodies (ANAs), anti-double-stranded DNA (anti-dsDNA), antinucleosome, antihistone, and anti-extractable nuclear antigen (anti-ENA) antibodies in rheumatoid arthritis (RA) and spondylarthropathy (SpA) patients. METHODS: Sera from 62 RA and 35 SpA patients treated with infliximab were tested at baseline and week 30 (RA group) or week 34 (SpA group). ANAs were tested by indirect immunofluorescence (IIF) on HEp-2 cells. Anti-dsDNA antibodies were detected by IIF on Crithidia luciliae and by enzyme-linked immunosorbent assay (ELISA) and were further isotyped with gamma, mu, and alpha chain-specific conjugates at various time points. Antinucleosome antibodies were tested by ELISA. Antihistone and anti-ENA antibodies were detected by line immunoassay. RESULTS: Initially, 32 of 62 RA patients and 6 of 35 SpA patients tested positive for ANAs. After infliximab treatment, these numbers shifted to 51 of 62 (P < 0.001) and 31 of 35 (P < 0.001), respectively. At baseline, none of the RA or SpA patients had anti-dsDNA antibodies. After infliximab treatment, 7 RA patients (P = 0.016) and 6 SpA patients (P = 0.031) became positive for anti-dsDNA antibodies. All 7 anti-dsDNA-positive RA patients had IgM and IgA anti-dsDNA antibodies. Three of the 6 anti-dsDNA-positive SpA patients had IgM and IgA anti-dsDNA antibodies, and 2 had IgM anti-dsDNA antibodies alone. In both diseases, the IgM anti-dsDNA antibodies appeared before the IgA anti-dsDNA antibodies. During the observation period, no IgG anti-dsDNA antibodies or lupus symptoms were observed. The development of antinucleosome, antihistone, or anti-ENA antibodies following infliximab treatment was observed in some patients, but the numbers were not statistically significant. CONCLUSION: Infliximab treatment may induce ANAs, and especially IgM and IgA anti-dsDNA antibodies, in RA and SpA patients. However, no anti-dsDNA IgG antibodies or lupus symptoms were observed during the period of observation in this study, and the development of antinucleosome, antihistone, or anti-ENA antibodies was not statistically significant. These observations do not exclude potential induction of clinically significant lupus in the long term, and further followup is therefore mandatory.     

Immune deposits in articular cartilage of patients with rheumatoid arthritis have a granular pattern not seen in osteoarthritis

Summary Frozen sections of articular cartilage, obtained from patients with rheumatoid arthritis (RA) or osteoarthritis (OA) undergoing joint replacement, were stained with fluoresceinated specific antisera to IgG, IgM, IgA, C1q, C4, and C3. Specimens positive for IgG were examined for IgG subclasses using mouse monoclonal antibodies. IgG was present in 22 of 34 cartilage specimens obtained from patients with RA, and in 14 of these 22 patients, a granular pattern was present. IgM, IgA, C1q, and C3 when present showed a similar granular pattern. In articular cartilage of patients with RA, all IgG subclasses tended to be present. The remaining eight specimens positive for IgG from patients with RA had staining patterns also seen in patients with OA. IgG staining was present in 31 of 117 cartilage specimens obtained from patients with OA and none had the granular pattern seen in RA. Intermittent linear staining at the surface was the most common pattern seen in cartilage from patients with OA. The different patterns of immune deposits in articular cartilage in RA and OA suggest that antibodies with different specificities are present or that different mechanisms of immune deposit formation exist in these disorders.     

High diagnostic value in rheumatoid arthritis of antibodies to the stratum corneum of rat oesophagus epithelium, so-called ''antikeratin antibodies''.

Serum antibodies to the stratum corneum of rat oesophagus epithelium, so-called 'antikeratin antibodies', have been largely demonstrated in rheumatoid arthritis (RA). IgM and IgG antibodies to this epithelium were studied by semiquantitative immunofluorescence in 528 patients with perfectly characterised rheumatic diseases, including 178 with classical or definite RA. Histological analysis of IgG antibodies showed that only antibodies which produce a linear laminated pattern restricted to the stratum corneum (IgG antikeratin antibodies) are highly specific for RA; all the other labelling patterns are not disease specific. By a semiquantitative evaluation of the stratum corneum fluorescence intensity it was shown that the diagnostic value of IgG antikeratin antibodies closely depends on their titre and it was established in objective conditions that the sensitivity is 43.26% when the specificity reaches 99.14%. A high titre of IgG antikeratin antibodies was actually pathognomonic for RA. Both the histological and semi-quantitative analyses showed that IgM antibodies to rat oesophagus epithelium, though frequently detected, are of no diagnostic value, either for RA or for any other rheumatic disease that was studied. From a review of all the international reports on IgG antikeratin antibodies it was found that, to date, 4080 patients, including 1694 with RA, have been assayed for antikeratin antibodies by 11 different research groups. Analysis of all the results obtained under comparable technical conditions showed that IgG antikeratin antibodies constitute the most specific serological criterion for the diagnosis of RA. Furthermore, it was found that their incidence does not depend on disease duration: they are present in one third of rheumatoid factor negative patients with RA, and they seem to be related to disease severity or activity, or both. Their detection in the diagnosis of rheumatic diseases should become systematic.     

Differential reactivity of rheumatoid synovial cells and serum rheumatoid factors to human immunoglobulin G subclasses 1 and 3 and their CH3 domains in rheumatoid arthritis

19S IgM rheumatoid factors (RF) are polyclonal autoantibodies that may play an important pathogenic role in sustaining inflammatory synovitis in rheumatoid arthritis (RA). RF in RA have reactivity for as-yet-uncharacterized antigenic determinants in IgG Fc. We hypothesized that qualitative differences might exist between some of these RF molecules, and that differences such as reactivity and affinity might characterize more pathogenic RF molecules. Previous observations in our laboratory indicate that RF produced by rheumatoid synovial cells (RSC) have greater reactivity with human IgG and IgG3 subclass, in contrast to serum RF, which has greater reactivity with rabbit IgG and human IgG1. These observations were made using a complement-dependent RF plaque-forming cell assay. The purpose of this study was to validate and extend those observations. Therefore, we examined the reactivity of RSC and serum RF with human and rabbit IgG and the reactivity and avidity of RSC-RF for IgG1 and IgG3 molecules and Fab, F(ab')2, and pFc' fragments thereof in a solid-phase enzyme immunoassay. In particular, we found: RSC-RF had at least twice as much reactivity with human IgG as with rabbit IgG; serum RF had approximately equal reactivity with human and rabbit IgG; RSC-RF had greater reactivity and avidity for IgG3 and IgG3 pFc' than for IgG1; and RSC-RF was nonreactive with Fab or F(ab')2 from either IgG1 or IgG3. These results suggest that the major antigenic determinant for RSC-RF resides in the CH3 domain of the IgG3 molecule. Precise characterization of this epitope may provide further insight into the etiology and pathogenesis of RA.     

Immunoglobulins, anti-IgG antibodies and antinuclear antibodies in paired serum and synovial fluid samples. A comparison between juvenile and adult rheumatoid arthritis

Paired samples of serum and synovial fluid (SF) from 13 patients with juvenile rheumatoid arthritis (JRA) and 10 patients with adult rheumatoid arthritis (RA) were examined regarding the level of immunoglobulins and the occurrence and titres of anti-IgG antibodies and antinuclear antibodies (ANA). The levels of immunoglobulins were lower in SF than in serum. In JRA the SF/serum ratio of IgG was equal to that of albumin, pointing to a local production of IgG. The SF/serum ratio of IgM was equal to that of alpha 2-macroglobulin. In JRA the SF/serum ratios of immunoglobulins tended to be lower than in RA, the difference being significant for IgM. IgD autoantibodies and IgA anti-IgG were not found in JRA. IgE autoantibodies occurred in some cases, but in RA in more than 60%. In JRA the SF titres of anti-IgG and ANA were most often lower than the serum titres. In RA the SF titres were often higher than the serum titres. In 9 of 10 paired SF samples from patients with RA the SF/serum ratios were mutually different with regard to one or several immunoglobulins. Evidence of synovial production of anti-IgG antibodies of classes other than IgG distinguished RA from JRA. Otherwise the differences were quantitative.     

ELISA test for antimeningococcal IgG and IgM antibodies: application to epidemiology and diagnosis.

We have developed an enzyme-linked immunosorbent assay (ELISA) in order to quantitate antimeningococcal IgM and IgG serum antibodies. The B:15 meningococcal strain was used as coating antigen, and class specific antibodies were detected by using alkaline phosphatase labelled rabbit anti-human IgM or IgG as conjugate. The specific IgG activity was higher in sera from healthy meningococcal carriers than non-carriers, but the difference was not statistically significant. Antimeningococcal IgM serum antibodies were more frequent in carriers that in non-carriers. Acute sera from 34 patients with fulminant meningococcal disease contained less specific IgG and had a higher prevalence of IgM than healthy carriers and non-carriers. By combining measurement of antimeningococcal IgG and IgM antibodies in both acute and convalescent sera 15/18 meningococcal patients demonstrated an increase in either IgG and IgM antibodies during the hospital stay, giving a sensitivity of 83%. 8/118 individuals without meningococcal disease had detectable specific IgM antibodies in their serum, giving a clinical specificity of the test of 93%. We conclude that quantitation of specific IgG antimeningococcal antibodies by a whole bacteria ELISA test may be a useful test for the study of immunity against meningococcal disease in single individuals as well as in epidemiological studies. The combined use of the IgG and IgM tests is helpful in the diagnosis of meningococcal disease when blood or cerebrospinal fluid cultures are negative.     

Antibodies to cultured rat heart cells in sera of patients with rheumatoid arthritis.

Since heart lesions occur in many patients with rheumatoid arthritis (RA), sera from these patients were tested with an indirect fluorescent technique for antibodies reactive with rat heart cell cultures. Of 27 sera 22 had reactivity with non-muscle (nM) cells and 3 reacted with cultured beating muscle cells (M). Positive sera reactive with nM cells exerted complement-dependent cell cytotoxicity towards M cells. The nM antibodies were found to belong predominantly to the IgG class. They displayed no cross-reactivity with bovine collagen, human and bovine serum proteins, or human and sheep red blood cells. The relationship of these antibodies to the pathogenesis of RA heart lesions remains to be determined.     

Antibodies to neuroblastoma cells in rheumatoid arthritis: a potential marker for neuropathy

OBJECTIVE: To investigate the prevalence of antibodies to neuroblastoma cells in patients with rheumatoid arthritis (RA) complicated by peripheral neuropathy (PN), and to determine whether there is any relationship of these antibodies with the severity of neuropathy. METHODS: The study was carried out on 28 patients with RA complicated by PN, 29 RA patients without PN and 28 healthy volunteers (HV). A cell-based ELISA method was used to test sera for the presence of IgG and IgM anti-neuroblastoma cell antibodies. Localisation and characterisation of neuroblastoma antigens recognised by patients' sera was carried out by immunofluorescent microscopy and Western blotting. RESULTS: Elevated levels of IgG anti-neuroblastoma cell antibodies were found in 10 (36%) neuropathic patients and in 1 (3%) RA control (chi 2 = 9.53, P = 0.002), while significant levels of IgM anti-neuroblastoma cell antibodies were demonstrated in 10 (36%) neuropathic patients and in 2 (7%) RA controls (chi 2 = 7.12, P = 0.008). Overall, the levels of antibodies in healthy volunteers were significantly lower than in RA controls and patients with PN. No significant relationship was found between the level of anti-neuroblastoma cell antibodies and severity of RA or neuropathy. Immunofluorescence staining of neuroblastoma cells with sera from 18 neuropathic patients demonstrated cytoplasmic and/or nuclear patterns. Western blotting demonstrated reactivity with a heterogeneous group of neuroblastoma antigens. Little or no reactivity was seen with RA control or HV sera. CONCLUSION: Antibodies against neuroblastoma cells are more prevalent in RA patients with peripheral neuropathy than in RA patients without peripheral nerve involvement. Such antibodies may be useful diagnostic markers for peripheral neuropathy in RA.