Antibody responses to the 18-kDa protein of Mycobacterium leprae in leprosy and tuberculosis patients.

The 18-kDa protein of Mycobacterium leprae, as recognized by the monoclonal antibody L5, has a restricted species distribution, being confined to M. leprae and M. habana. We have developed a solid-phase ELISA using purified, recombinant M. leprae 18-kDa protein and compared the serological responses of Nepali leprosy and tuberculosis patients and endemic control subjects to the protein and the M. leprae phenolic glycolipid-I (PGL-I). Few control subjects had anti-18-kDa antibodies. A small proportion of paucibacillary (PB) leprosy and 42% of multibacillary (MB) leprosy patients had IgG anti-M. leprae antibodies. A similar proportion (47%) of Nepali tuberculosis (TB) patients were seropositive, and IgG anti-18-kDa antibody levels were significantly higher in MB and TB patients than in control subjects. By comparison, IgM anti-PGL-I antibodies were detected in 88% of MB leprosy patients and only 7% of TB patients. The possible reasons for the 18-kDa protein seroreactivity in TB patients are discussed, and the anti-18-kDa assay is compared with other antibody assays for protein and nonprotein antigens of M. leprae. It is concluded that the sensitivity and specificity of the anti-M. leprae 18-kDa ELISA are insufficient for the assay to be of clinical utility in leprosy patients.     

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.     

Analysis of Toxoplasma gondii antigens recognized by human sera obtained before and after acute infection

The antibody response to Toxoplasma gondii was studied in human serum samples obtained before and during acute infection with T. gondii. Analysis was by the Sabin-Feldman dye test, double-sandwich IgM ELISA, agglutination test, and protein blots of toxoplasma antigens. Seventeen patients were studied: 12 pregnant women, 2 heart transplant recipients, and 3 symptomatic but immunologically normal individuals. Both IgM and IgG protein blots of the first serologically positive serum sample from each patient revealed new bands, as well as intensified staining of bands noted with the serologically negative serum samples. In each patient, bands corresponding to antigens of approximately 4 kilodaltons (kDa; IgM blots) and of approximately 35 kDa (IgG) were the most intensely stained. In one patient, IgM antibodies to the 4-kDa antigen(s) were demonstrable by protein blots before they were demonstrable by IgM ELISA. IgG protein blots of sera from individuals with chronic infection with T. gondii revealed weakly reactive antibodies to both the 4-kDa and 35-kDa antigens; these bands were not demonstrable in the IgM blots.     

Salivary immunoglobulins and antibody activities in leprosy

The technics of immunodiffusion and the fluorescent leprosy antibody absorption (FLA-ABS) test were used to determine the levels of immunoglobulins and their antibody activities against Mycobacterium leprae in the serum and the saliva collected from a total of 110 patients with leprosy (50 lepromatous, 24 borderline, and 36 tuberculoid). The average levels of serum IgG, IgM, and IgA were not significantly different among these patients. In saliva, however, IgM was detected in only two cases with lepromatous leprosy and three tuberculoid cases. Salivary IgG and IgA levels and their ratios to those in the sera were not significantly different according to the classification of leprosy. The percentages of positive FLA-ABS tests in the sera and saliva were compared by using fluorescent antibodies specific for IgG, IgM, and IgA, respectively. The results indicated that M. leprae-specific antibodies in the serum were mainly found in IgG and IgM and, less frequently, in IgA. IgG antibodies were found more frequently in lepromatous and borderline patients than in tuberculoid cases. On the other hand, salivary IgA antibodies against M. leprae were found in a significant number of specimens; whereas IgG and IgM antibodies were scarcely found. However, the percentage of positive FLA-ABS tests caused by salivary IgA antibodies was higher in the patients with tuberculoid or borderline leprosy than in those with lepromatous leprosy. A significant number of patients with tuberculoid or borderline leprosy secreted M. leprae-specific IgA antibodies into saliva without detection of circulating IgA antibodies.(ABSTRACT TRUNCATED AT 250 WORDS)     

Immunological assessment of sera of leprosy patients.

IgG levels were significantly high in sera of all types of leprosy. House-hold contacts of lepromatous leprosy (LL) cases also showed significantly higher values for IgG when compared to that of control. Except polar tuberculoid (TT) cases and house-hold contacts other types of leprosy revealed a significant rise in IgA levels in their sera. IgM was only raised in borderline tuberculoid (BT) cases. C-reactive protein (CRP) was present in the sera of all types of leprosy. Highest positivity (97%) was shown by sera from erythema nodosum leprosum (ENL) cases. Rose-Waaler antibody (RA) was noted in BT, borderline leprosy (BL), LL and ENL cases. Significance of these findings is discussed.     

Specific anti-M leprae PGL-I antibodies and Mitsuda reaction in the management of household contacts in New Caledonia

Household contacts of leprosy patients have been tested for anti-phenolic glycolipid-I IgM antibodies (anti-PGL-I IgM) by an ELISA using the natural disaccharide (NDO) and natural trisaccharide (NTO) synthetic antigens. A group of healthy subjects without known exposure to Mycobacterium leprae served as controls. The percentages of positivity observed in multibacillary patients, paucibacillary patients, and household contacts were significantly higher than those of the negative controls. The absorbance values using NDO and NTO correlated well (range 0.59-0.91) when analysis of each subject group was performed. As reported here, NDO and NTO antigens seem to be equal in detecting leprosy cases; 100% of multibacillary and 21.43% of paucibacillary cases were detected as seropositive. For the screening of household contacts, NDO appears to be more sensitive and NTO more specific. There were more seropositive cases in the young age groups of household contacts, suggesting a higher rate of transmission of M. leprae infection in those age groups. Lepromin and anti-PGL-I IgG tests were also performed in contacts who were followed. The 2 paucibacillary subjects (1 borderline tuberculoid, 1 indeterminate) were Mitsuda negative. At diagnosis, their anti-PGL-I IgM levels were much higher than those of previous results; their anti-PGL-I IgG levels showed an increase in one and a decrease in the other. However, for the entire group anti-PGL-I IgM and anti-PGL-I IgG levels were positively correlated. The data reported here suggest that an increase in specific anti-M. leprae IgM levels in Mitsuda-negative household contacts could reveal the development of overt disease.     

BALB/c小鼠感染日本血吸虫后血清中SEA特异性抗体的动态观察

目的 观察BALB/c小鼠感染日本血吸虫后18周内血清中可溶性虫卵抗原 （SEA） 特异性IgG、 IgM抗体水平的动态变化。方法 尾蚴感染BALB/c小鼠, 感染2周后开始每周采血并分离血清, 以SEA为抗原, 通过ELISA测定不同感染时间血清IgG、 IgM值; 通过免疫印迹法检测不同感染时间小鼠血清中SEA特异性IgG、 IgM抗体条带。结果 ELISA检测结果表明感染小鼠血清IgG水平在感染5、 6、 9、 11周上升明显; IgM在感染5周和9周时上升明显。免疫印迹试验结果表明感染血吸虫4周后, 小鼠血清中开始出现140、 180、 210 kDa蛋白特异性IgG抗体; 感染5周后出现43、 50 kDa强反应IgG特异性抗体带; 感染6周后在60～130 kDa处出现 IgG特异性弥散带; 感染9周后出现38、 73 kDa 蛋白特异性IgG条带, 其中38 kDa 条带较弱, 随感染时间延长, 条带反应逐渐增强, 直至感染18周; 感染11周后新增26、 32、 35、 80 kDa特异性IgG条带, 并且在12周后增强。感染3周后出现100、 140、 180 kDa IgM特异性反应条带, 感染9周后出现73 kDa特异性IgM强反应条带及 38、 43、 50 kDa弱反应IgM抗体带, 后3条蛋白条带随感染时间延长逐渐变强。 结论 SEA中不同组分抗原对感染宿主的免疫调节具有时间特异性, 其中43、 50、 100、 140、 180 kDa具有早期诊断价值; 73 kDa 既可用于急性血吸虫病诊断, 也可用于慢性血吸虫病诊断; 28、 32、 35、 38、 80 kDa抗原既可作为慢性血吸虫感染的优势抗原, 同时也可能具有一定的抗血吸虫感染作用, 可作为疫苗开发的候选抗原。     

Specific and early detection of IgG, IgA and IgM antibodies to Mycobacterium tuberculosis 38kDa antigen in pulmonary tuberculosis

The objective was to apply the purified 38kDa protein antigen of Mycobacterium tuberculosis in ELISA to estimate the IgG, IgA and IgM antibody levels in sera and circulating immune complexes of tuberculosis patients. Sera from smear and culture positive tuberculosis patients were positive for anti 38kDa IgG, IgA and IgM antibodies, with a sensitivity of 61%, 30% and 10%, respectively, and with a specificity of 100% for IgG. The sensitivity of the test improved to a level of 68% for IgG+IgA and of 71.4% for IgG+IgA+IgM without significantly compromising the specificity (IgG of 100%, IgG+IgA of 96%, IgG+IgA+IgM of 90%). Among the smear, culture-negative but X-ray-positive cases, 60% were serum positive for IgG antibody, while in smear-negative but culture-positive cases, 54% were positive for IgG antibody. Measurement of 38kDa antibodies showed a greater than 95% sensitivity in smear and culture-positive, and smear-negative and culture-positive patients, through a combination of assays for serum IgG and circulating immune complex antibodies, while the specificity was 100%.     

Sero-immunoreactivity of cloned protein antigens of Mycobacterium leprae.

Sera from 173 leprosy patients with various types of disease (tuberculoid = TT, borderline tuberculoid = BT, borderline lepromatous = BL, and lepromatous = LL), 12 intrafamilial contacts, and 40 normal healthy individuals were assayed in an indirect enzyme-linked immunosorbent assay (ELISA) using Mycobacterium leprae antigens. Recombinant clones carrying M. leprae antigens, namely, Y3184 (12 kDa), Y3179 (18 kDa), Y3164 (28 kDa), Y3180 (36 kDa), and Y3178 (65 kDa) and a cell sonicate from armadillo-derived M. leprae were used for the study. A high degree of reactivity with the 65-kDa, 36-kDa, and 28-kDa protein lysates was observed in most of the sera from multibacillary patients, with a low degree of positivity with 18 kDa and 12 kDa. Only a few sera from paucibacillary patients showed positive reactions. The majority of the contacts' sera tested showed no reactivity with these antigens.     

THE SEROLOGICAL RESPONSE TO THE PHENOLIC GLYCOLIPID OF MYCOBACTERIUM LEPRAE IN AUSTRALIAN AND NEPALI LEPROSY PATIENTS

Abstract Antibodies to the species-specific phenolic glycolipid (PGL-1) of Mycobacterium leprae and a crude M. leprae sonicate were measured by ELISA in sera from newly diagnosed and treated leprosy patients from Sydney and Nepal. IgM anti-PGL-1 antibodies were present in 88–90% of untreated patients at the lepromatous pole of the clinical spectrum and 35–55% of those at the tuberculoid pole. In treated patients with either form of the disease, IgM anti-PGL-1 antibodies were within the normal range or minimally elevated. In contrast, high levels of IgG anti-PGL-1 antibodies were detected in both treated and untreated patients. Neither IgM nor IgG anti-PGL-1 antibodies were elevated in sera from Mantoux negative controls and only one out of 15 sera from patients with untreated tuberculosis contained significant amounts of antibody. Comparison of the data from the anti-PGL-1 assay with the antibody response to a crude M. leprae sonicate revealed that the latter assay yielded more variable results and discriminated less well between lepromatous and tuberculoid subjects and between untreated patients and those on therapy. Thus the IgM anti-PGL-1 response signifies the presence of active disease, particularly in multi-bacillary cases, and has the potential to be used not only to monitor the response of these patients to therapy, but also to detect subclinical leprosy in high-risk groups such as the relatives of patients with lepromatous disease.     

Antibodies to HIV-1 in sera from patients with mycobacterial infections

Sera from 478 persons (348 leprosy patients, 33 tuberculosis patients, 29 healthy contacts of leprosy patients, 38 normal healthy Indians, and 30 normal healthy Europeans) were screened for anti-HIV-1 IgG antibodies by ELISA. None was positive. In addition, 132 samples (from 43 leprosy patients, 21 tuberculosis patients, 5 healthy contacts of leprosy patients, 33 normal healthy Indians, and 30 normal healthy Europeans) were also tested by Western blot assay for anti-HIV-1 IgG antibodies. Only 1 of the 63 healthy subjects expressed a prominent p17 band. One or more bands were found in 44 (leprosy patients 33/43, tuberculosis patients 7/21, and leprosy contacts 4/5) of the remaining 69 sera. Antibody to the HIV-1-specific antigen p24 was expressed by 17 of these subjects (14/43 leprosy patients, 1/21 tuberculosis patients, and 2/5 leprosy contacts), either as a single band or in combination with other bands. This raises the possibility of a common antigenic pattern between HIV-1 and mycobacteria, especially Mycobacterium leprae.     

Borrelia burgdorferi (strain B. afzelii) antibodies among Malaysian blood donors and patients

In this study, the presence of IgG and IgM antibodies against Borrelia burgdorferi (strain B. afzelii) among Malaysian blood donors and patients admitted to hospital with various infectious diseases was determined. Sera were screened using enzyme-linked immunosorbent assay (ELISA); positive sera were then subjected to Western blot testing. All but one of the blood donors were negative for borrelial antibodies. Of 121 patients' sera, IgM antibodies were detected in 24 (19.8%) and IgG antibodies were detected in 5 (4.1%) sera. Only one of two patients with skin manifestations suggestive of Lyme disease had IgM antibody against B. afzelii. Of 30 patients with exposure to tick typhus, 4 (13.3%) were IgM positive and 1 (3.3%) was IgG positive. Based on the detection of antigenic bands by Western blot, 6 patients' sera showed positive reactions. Antigenic bands of p39, p41 and p59/62 kDa were the commonest findings of Western blotting. This study provides serological evidence of B. afzelii infections in Malaysia; further investigation is needed to correlate serological and clinical findings.     

Identification of Trichomonas vaginalis alpha-actinin as the most common immunogen recognized by sera of women exposed to the parasite.

A study on presence of antibodies to Trichomonis vaginalis in serum was done on a group of 500 pregnant, asymptomatic Angolan women. A serologic screening, done by ELISA, revealed that 41% of the women had IgG and IgM against the parasite. Analysis of sera by immunoblotting revealed that 94.4% of sera with anti-T. vaginalis IgG class antibodies were reactive against a common immunogenic protein of 115 kDa. The common immunogen was identified as the protozoan alpha-actinin. All sera recognizing the 115-kDa antigen were reactive against both native and recombinant T. vaginalis alpha-actinin and nonreactive against human alpha-actinin. The findings presented in this work offer a new tool for epidemiologic studies and open new perspectives for vaccination.     

Antibody response in pulmonary tuberculosis against recombinant 27kDa (MPT51, Rv3803c) protein of Mycobacterium tuberculosis

The objective of this study is to evaluate the recombinant 27kDa (MPT51, Rv3803c) antigen of M. tuberculosis H37Rv, expressed in E. coli in enzyme linked immunosorbent assays (ELISA) to estimate the IgG, IgA and IgM levels in sera from adult pulmonary tuberculosis patients and control groups. Sera from smear and culture positive tuberculosis patients (S + C +) were positive for anti-MPT51 IgG, IgA and IgM, with a sensitivity of 57%, 47% and 13%, respectively. The sensitivity of the test improved to a level of 71% for IgG+IgA without significantly compromising the specificity (IgG of 98%, IgG+IgA of 95%). Addition of IgM results did not enhance the sensitivity appreciably, over and above that of IgG+IgA (72% vs 71%). Among the smear-negative but culture-positive cases (S-C+), 34% were positive for IgG, while in smear and culture-negative but X-ray-positive cases (S-C-), 42% were positive for IgG. Polyethylene glycol precipitation (PEG) of the circulating immune complex (CIC) in sera was carried out. The CIC-bound antibodies to MPT51 were assessed using ELISA. Measuring the IgG+IgA combination positivities of the CIC-bound antibodies gave a poor sensitivity of 21%, 18% and 10%, respectively. The specificity of the assay by these combinations was maintained at 94%.     

Detection of specific circulating antigen, immune complexes and antibodies in human hydatidosis from Turkana (Kenya) and Great Britain, by enzyme-immunoassay

Circulating antigen, specific immune complexes (IgG and IgM) and specific antibodies (IgG, IgM, IgE and IgA) were detected by enzyme-linked immunosorbent assay (ELISA) in the sera of hydatid (Echinococcus granulosus) patients from Turkana (Kenya) and the UK. Specific IgG and IgM antibodies predominated in current UK hydatid infections, while all classes of specific antibodies were lower in the Turkana patients. Circulating antigen, detected in 3% polyethylene glycol (PEG) precipitated complexes, using peroxidase conjugated hyperimmune human hydatid IgG (Fab) was more specific in ELISA than either antibody or immune complex assays where peroxidase conjugated anti-human IgG was used. Anti-human immunoglobulin ('rheumatoid' factor) was not detected in hydatid sera. Serum antigen, specific IgM immune complexes and specific IgM antibodies were associated with UK cases of current hydatid infection in contrast to patients with previous histories of hydatidosis. In 3 hydatid patients (from UK) levels of circulating antigen and specific IgM immune complexes rapidly declined within 1-4 months after surgical cyst removal. The detection of specific IgG and antigen in PEG precipitated immune complexes from false-negative/low responder Turkana hydatid sera, suggests that antibody 'mopping' by specific antigen may be occurring. After SDS-PAGE/immunoblotting analysis, antigen of mol. wt 67 000, present in hydatid cyst fluid and protoscoleces, was identified as putative circulating antigen in 3% PEG precipitates of sera from albendazole treated hydatid patients.     

Recognition of Treponema pallidum antigens by IgM and IgG antibodies in congenitally infected newborns and their mothers

Immunoblotting techniques were used to examine the proteins of Treponema pallidum recognized by IgM and IgG antibodies in sera from infants with congenital syphilis and their mothers. Infected infants' serum IgM reactivity to treponemal antigens differed from that of control infants born to normal, serofast, and biologic false-positive mothers. Each of the infected infants' sera exhibited IgM reactions to the 47- and 37-kilodalton (kDa) proteins of T. pallidum. Although rheumatoid factor was detected in the sera of half of the infected infants, removing this factor did not alter the pattern of IgM blots. IgG reactions in infants were almost exclusively of the IgG1 and IgG3 subclasses and mirrored those of the mother, except for IgG1 and IgG3 reactions to the 83-kDa treponemal protein, which were unique to infants' sera. Our results suggest that the findings of IgM antibody directed against the 47- or 37-kDa antigens of T. pallidum may help to diagnose congenital syphilis at birth.     

Rapid serologic diagnosis of dengue virus infection using a commercial capture ELISA that distinguishes primary and secondary infections.

A commercial capture ELISA for specific IgM and IgG antibodies produced during dengue infection (PanBio Dengue Duo) showed excellent sensitivity (99%, n = 78) using sera collected at hospital discharge compared with established ELISA and hemagglutination inhibition (HAI) assays. Furthermore, the ELISA was able to diagnose 79% of the dengue cases using sera collected at hospital admission. The ELISA also showed high specificity (92%) in paired sera from patients without flavivirus infection (n = 26), although 45% of the patients with Japanese encephalitis (n = 20) showed elevation of IgG but not IgM. The IgG capture ELISA showed good correlation with the HAI assay (r = 0.83, P < 0.0001), and IgG levels could be used to distinguish between primary and secondary infection, with 100% of primary infections and 96% of secondary infections being correctly classified. This ELISA should prove useful in the clinical diagnosis of dengue infections.     

Operational value of serological measurements in multibacillary leprosy patients: clinical and bacteriological correlates of antibody responses

The antibody responses of 100 previously untreated multibacillary (MB) leprosy patients to one protein and two carbohydrate antigens were examined: 94% of the patients had Mycobacterium leprae-specific antibodies; 89% directed to the species-specific epitope on phenolic glycolipid (PGL-I), 89% against the specific epitope on the 35-kDa protein, and 94% against one or both of the two. By contrast, 67% of the patients had anti-lipoarabinomannan (LAM) antibodies. There were trends for the seropositivity rate and the antibody level to rise with the increasing extent of the disease and as patients moved to the polar lepromatous end of the spectrum. The bacillary load, as measured by the bacterial index, was moderately correlated with the IgM anti-PGL-I and the anti-35-kDa antibody levels and, to a lesser extent, with the IgG antibodies directed at the common mycobacterial carbohydrate LAM. The sensitivity of the IgM anti-PGL-I antibodies for detecting smear-positive MB disease was 91%; that for the anti-35-kDa antibodies was 92%.     

Elevated IgM anti-IgE in sera from allergic patients.

The role of anti-IgE autoantibodies in IgE-related allergic diseases has not been elucidated sufficiently. For example, anti-IgE antibodies have been reported to cause both proallergic and antiallergic blocking reactions. Contrary to other authors, some authors revealed a positive correlation between total IgE and the amount of IgE/IgG complexes detected. By comparing the IgE levels of allergic patients with those of control persons and rheumatoid arthritis patients the present study contributes to our understanding of the role of anti-IgE autoantibodies. The sera were tested by means of ELISA concerning their content of free and complexed IgG and IgM anti-IgE. In addition, the amounts of IgE/IgG and IgE/IgM complexes were determined in the sera of allergic and control persons after Superose 6 column separation. We found that the allergic patients revealed significantly higher values of free IgM anti-IgE than patients with rheumatoid arthritis and than control persons (mean 0.470, p = 0.0164 and p = 0.0061, respectively). The corresponding values for IgE/IgM complexes also tend to be higher (mean 0.431, p = 0.0784 and p = 0.0601, respectively). However, the corresponding contents of IgG anti-IgE autoantibodies and IgE/IgG complexes did not differ significantly. After Superose 6 column separation, we detected IgE/IgG in fractions corresponding to MW of 150 to 180 kDa for the sera of both allergic and control persons. In contrast, the IgE/IgM complexes were found in fractions corresponding to MW 330 kDa. We conclude that the increased IgM anti-IgE autoantibody titer in the sera of allergic patients is not correlated with the high total IgE level. Moreover, we suggest that the IgE/IgG complexes form de nova during ELISA. Unlike the IgE/IgG complexes, the IgE/IgM complexes are assumed to occur already in circulating blood.     

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.