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At least 19 recordsLinked to original sources
PubMed1993

Molecular composition of two different batches of urofollitropin: analysis by immunofluorimetric assay, radioligand receptor assay and in vitro bioassay.

The molecular heterogeneity of two different batches of commercially available urofolitropin was analyzed after fractionation by isoelectric focusing (IEF). FSH was measured before and after IEF by a highly specific time-resolved immunofluorimetric assay (IFMA), by a radioligand receptor assay (RRA) employing a preparation of calf testis FSH receptors, and by the in vitro bioassay based on FSH-dependent aromatase stimulation in immature rat Sertoli cells. An overall good correspondence between the results obtained with the three different methods was observed. However, the RRA and the in vitro bioassay appeared to be more suitable than the IFMA in resolving individual FSH isoforms. The mean isoelectric points of the two FSH preparations analyzed were slightly different, due to different molecular composition. These differences, however, seem too minute to be considered as cause of the different pharmacokinetics of FSH described in the literature or to explain the inconsistent therapeutical results seen in patients treated with FSH of urinary origin.

Animals↗
PubMed1989

Assessment of antithyroglobulin and antimicrosomal autoantibodies in patients with autoimmune thyroid disease: comparison of haemagglutination assay, enzyme-linked immunoassay and radioligand assay.

Four different assay systems for detection of antithyroglobulin (T-Ab) and thyroid antimicrosomal autoantibodies (M-Ab) were evaluated: two passive haemagglutination assays (PHA), an enzyme-linked immunoassay (ELISA) and a radioligand assay (RLA). Antibody levels measured with these methods correlated well (T-Ab: r = 0.72 to 0.88; M-Ab: r = 0.63 to 0.84; p less than 0.0001). However, when the results of the measured samples were classified as normal, slightly elevated and pathological, only 40-50% of the samples showed congruous results in all tests; 60-70% agreed in PHA and ELISA, whereas 80 to 90% corresponded in the two PHAs. RLA and ELISA gave more frequently positive results for T-Ab and negative results for M-Ab than the PHAs. Despite the lower sensitivity of the quantitative methods for M-Ab detection, they depicted more readily small changes after thyroxine treatment than the PHAs. We suggest that differences in autoantibody levels found with different methods may be due to autoantibody heterogeneity.

Autoantibodies↗
PubMed1975

Radioligand assay in reproductive biology.

Radioligand assays have been developed for the principal reproductive steroids and peptide hormones. Specific binding reagents have included antibodies, plasma binders, and intracellular receptors. In each assay, problems of specificity, sensitivity, and nonspecific inhibitors were encountered. Many features of the endocrine physiology in childhood, during puberty, and in adulthood have been characterized. Hormonal evaluations of endocrine disorders of reproduction are characterized on the basis of their characteristic pathophysiologic alterations.

Adult↗
PubMed1997

A new approach to cytochrome CYP2D6 antibody detection in autoimmune hepatitis type-2 (AIH-2) and chronic hepatitis C virus (HCV) infection: a sensitive and quantitative radioligand assay.

Antibodies specific for cytochrome CYP2D6, formally known as liver-kidney-microsome type-1 antibodies (LKM-1), are characteristically found in a subgroup of patients presenting autoimmune hepatitis. They are also found in some patients with chronic HCV infection. These autoantibodies are usually detected by indirect immunofluorescence, immunoblotting and ELISA tests. In an attempt to set up a more sensitive detection assay we developed a quantitative immunoprecipitation radioligand assay using a 35S-methionine-labelled CYP2D6 antigen obtained by in vitro transcription and translation synthesis. All 16 sera from AIH-2 patients strongly bound to this CYP2D6 antigen. Two of the nine sera (22%) from AIH-2 patients that presented only liver cytosol-1 antibodies also bound to CYP2D6. All 24 sera from HCV patients that were positive for LKM-1 antibodies by indirect immunofluorescence were also positive using this CYP2D6 radioligand assay. Lastly, all 15 sera from HCV patients negative for LKM-1 antibodies were negative by this test. The present results support the view that this quantitative radioligand assay is more sensitive than immunoblotting and ELISA CYP2D6 assays, and that it could be used in combination with indirect immunofluorescence assay.

Adolescent↗
PubMed2004

[Improved radioligand assay of insulin autoantibody].

OBJECTIVE: To establish an improved radioligand assay of insulin autoantibody (IAA) and to investigate the diagnostic role of IAA in type 1 diabetes (T1DM). METHODS: 125I-insulin antigens were mixed with sera samples in the Eppendorf tubes. The immunocomplexes were precipitated with protein A-agarose, then washed with TBST buffer and counted the cpm value using liquid scintillation counter. The assay results were expressed by IAA index and compared with those of an international standardized laboratory and a domestic anti-insulin antibody kit. Sera of 32 recent-onset type 1 diabetic patients and 120 healthy controls were screened for IAA and the consistency, sensitivity, specificity and the diagnostic value of IAA were evaluated. RESULTS: (1) The intra-assay coefficient of variation (CV) was 5.8% - 8.3%, and the inter-assay CV 7.0% - 11.0%. The IAA indices of 41 samples tested in our laboratory and in an international standardized laboratory were strongly positively related (r = 0. 783, P < 0. 01) (100.0% concordance). Arrayed according to their antibody titers, the IAA indices of 82 samples measured in our laboratory and in a domestic anti-insulin antibody kit were also strongly positively related (r = 0.982, P < 0.0001) (89.0% concordance, Kappa value 0.813), but 9 samples were positive with low titer (index 0.05 - 1.00) by the radioligand assay or negative by the kit. 2) The IAA index cut-off point was determined according to the upper limit of 99.5% percentile of 120 healthy controls. The index of 0.051 or higher was defined as positive. The IAA positivity prevalence was 18.8% (6/32) in type I diabetes and 0.8% (1/120) in the healthy controls (P < 0.001). The positivity frequency of IAA was 28.6% (4/14) in patients younger than 15 years of age and the duration less than half a year, while 11.1% (2/ 18) in those older than 15. CONCLUSION: The improved radioligand assay for IAA has a high sensitivity and specificity and can be used in clinical practice, especially for the low-titer positive subjects.

Adolescent↗
PubMed2003

[Quality control of radioligand assay for glutamic acid decarboxylase antibody].

OBJECTIVE: To supply the quality control for glutamic acid decarboxylase antibody (GAD-Ab) measurement using radioligand assay. METHODS: The quality control of GAD-Ab determined with radioligand assay in 83 batches was analyzed. RESULTS: The intra-assay coefficient of variation (CV) was 4.3% to approximately 8.3% and the inter-assay CV was 7.1% to approximately 10.8%. A ratio of signal to noise (S/N) with 15 or more was defined as a valid measurement. Of the 83 batches, 67 batches (80.7%) met with the standard and the other 16 (19.3%) were not qualified. When the results were analyzed according to the season, the failure rate in summer was significantly higher than that in winter (38.5% vs 4.8%, P < 0.05). In addition, the mean value of S/N in summer was significantly lower than that in winter ( 14.1 +/- 7. 3 vs. 21.5 +/- 5.2, P < 0.01). Among the failed batches, 68.8% (11/16) was caused by TBST buffer and 50% (8/16) due to the increased temperature of TBST buffer. Other causes for the failure included the invalidation of reagents for in vitro transcription and translation. CONCLUSION: TBST buffer and other influential factors of radioligand assay in determining GAD-Ab, should be controlled strictly to ensure a reliable and repeatable result.

Autoantibodies↗
PubMed1998

Interferon therapy in LKM-1 positive patients with chronic hepatitis C: follow-up by a quantitative radioligand assay for CYP2D6 antibody detection.

BACKGROUND/AIMS: Liver/kidney microsomal type 1 (LKM-1) antibodies described by indirect immunofluorescence using frozen sections of kidney, stomach and rat liver define a group of patients with type 2 autoimmune hepatitis. Sera react with a non-glycosylated 50-kD protein of the endoplasmic reticulum, which was recently identified as cytochrome P4502D6 (CYP2D6). LKM-1 antibodies may also be associated with hepatitis C virus infection (HCV+/LKM-1+). For this subset of patients, the choice of steroids or interferon alpha therapy may be difficult because of the association of hepatitis C virus infection and autoimmune manifestations. Recently we developed a quantitative immunoprecipitation radioligand assay using 35S-methionine-labeled CYP2D6 protein produced by in vitro transcription and translation reaction. This method detects antibodies against linear and conformational epitopes in both AIH-2 and HCV+/LKM-1+ patients. The aim of this study was to analyze the time-course of HCV+/LKM-1+ patients, applying our radioligand assay over a long follow-up. METHODS: We studied five patients who were positive for CYP2D6 antibodies from among 235 chronic hepatitis C virus hepatitis patients (2.1%) treated with interferon alpha for a minimal follow-up of 2 years. We analyzed LKM-1 antibody titer sequentially by radioligand assay, HCV RNA titer and alanine aminotransferase activity in these patients. RESULTS: We found no aggravation of liver disease in this group of patients. Three of these patients showed a sustained biochemical and virological response after interferon. Two others responded partially to interferon therapy. Alanine aminotransferase levels and HCV-RNA decreased during interferon therapy in responder patients. CYP2D6 antibodies did not change in three responder patients during follow-up. One responder patient decreased CYP2D6 antibody level by radioligand assay, but indirect immunofluorescence titers showed a similar pattern. One partial responder patient decreased CYP2D6 antibody level but was negative by indirect immunofluorescence. CONCLUSIONS: Our results show that patients with hepatitis C virus who are positive for CYP2D6 antibodies may be treated with interferon, and respond in the same way as CYP2D6 antibody negative patients. Radioligand assay could be helpful for monitoring HCV+/LKM-1+ patients receiving interferon therapy.

Adult↗
PubMed2002

Anti-CYP2D6 antibodies detected by quantitative radioligand assay and relation to antibodies to liver-specific arginase in patients with autoimmune hepatitis.

BACKGROUND: Antibodies to cytochrome P4502D6 (CYP2D6) were measured and their prevalence compared with that of antibodies to liver-specific arginase in patients with autoimmune hepatitis (AIH). METHODS: Anti-CYP2D6 antibodies were measured by sensitive radioligand assay and enzyme-linked immunosorbent assay (ELISA), and anti-arginase antibodies were measured by ELISA in 132 patients (definite AIH 11, probable AIH 36, hepatitis C 20, hepatitis B 23, other autoimmune diseases 42) and 50 healthy controls. RESULTS: CYP2D6 index (radioligand assay) was significantly higher in all groups of patients than those in healthy controls. A higher index than the cut-off value (mean+3 S.D. in healthy controls) was found in 36.4%, 44.4%, 25.0%, 17.4% and 28.6% of patients with definite AIH, probable AIH, hepatitis C, hepatitis B and other autoimmune diseases, respectively. CYP2D6 index was not related to serum IgG, anti-nuclear antibody or AIH scores, and was weakly correlated with anti-arginase antibody activity. When CYP2D6 index and anti-arginase antibodies were combined, 55.3% of AIH patients were positive for either one or both antibodies. CONCLUSIONS: Anti-CYP2D6 antibodies by radioligand assay were frequently present in patients with AIH. Combined tests for anti-CYP2D6 radioligand assay and anti-arginase antibodies resulted in detection of 55% of AIH patients.

Antibody Specificity↗
PubMed1994

Comparison of radioligand assay and immunostaining for epidermal growth factor receptor in human breast cancer.

Epidermal growth factor (EGF) receptor status is a useful prognostic indicator in women with breast cancer. Lack of standardization and correlation of methodology for the detection of EGF receptor has hampered its further evaluation. EGF receptor status was ascertained by immunohistochemistry and radioligand assay in 120 breast cancers. Of 52 tumours negative for EGF receptor on radioligand assay, 47 were negative on immunohistochemistry and, of 68 tumours positive for the receptor on assay, 52 were positive on immunohistochemistry. If the more widely evaluated radioligand assay is assumed to be the 'gold standard', immunohistochemistry has a sensitivity of 81 per cent and a specificity of 91 per cent.

Biomarkers, Tumor↗
PubMed2005

Detection by radioligand assay of antibodies against Borna disease virus in patients with various psychiatric disorders.

Using a radioligand assay, which preserves the natural form of the antigen, antibodies against Borna disease virus nucleoprotein and phosphoprotein were detected in 11 and 19 sera of 171 psychiatric patients, respectively. Compared with results by Western blotting, three and nine sera were concordantly positive, respectively. The four sera showing the highest levels of antibodies by radioligand assay were all negative by Western blotting; however, dilution and inhibition tests supported the positive results. Our results suggest the importance of conformational structure to detect human anti-Borna disease virus antibodies.

Antibodies, Viral↗
PubMed1999

Antibodies to human recombinant tissue transglutaminase measured by radioligand assay: evidence for high diagnostic sensitivity for celiac disease.

Celiac disease is associated with endomysial antibodies (EmA), which have recently been reported to be directed to tissue transglutaminase (tTG). To demonstrate binding of antibodies to recombinant tTG, human tTG was cloned, expressed by in vitro transcription/translation and used to develop novel radioligand assays for combined and single detection of immunoglobulin A (IgA) and G (IgG)-specific antibodies. IgA and IgG-tTGA were found in 43 (95.6%) of 45 patients with newly-diagnosed celiac disease verified by biopsy. In addition, all 30 sera from patients with gastrointestinal symptoms and positive EmA were positive for IgA-tTGA, and all but one serum (96.7%) had antibodies of the IgG class. Receiver-operating characteristic analysis including 574 sera from healthy controls revealed a specificity of 99.5%. By means of these new assays, we identified all patients with endomysial antibodies and achieved, at equal specificity, an even improved sensitivity (95.6%) as compared to EmA (91.1%) detected by the standard immunofluorescence test. Here, we have provided direct evidence that recombinant tTG is a major target of antibodies in celiac disease. Our data suggest that tTGA measured by radioligand assay have the power to overcome the limitations of the EmA-test. This new strategy may considerably facilitate large-scale screening for silent and latent celiac disease.

Adolescent↗
PubMed1980

Radioligand assay for gonadotropin-releasing hormone: relative potencies of agonists and antagonists.

A radioligand assay employing tritiated gonadotropin-releasing hormone, [3H-Pro9]GnRH or [3H-pGlu1]GnRH is used to investigate the binding of GnRH, its agonists, and its antagonists to male rat anterior pituitary homogenates. The tritiated GnRH purified by high pressure liquid chromatography and stored in 10 mM HOAc is stable for binding for at least 14 weeks. It is found that there is at least one high affinity site with an observed Kd of congruent to 2 nM and another low affinity site whose Kd is congruent to 1 microM. Only approximately 25% of the total specific binding is to the low affinity site. At room temperature, the binding is reduced to 50% of that at 0 C, and at 37 C, there is no measurable binding. Bacitracin has no effect on the binding at any temperature. Maximum binding occurs between pH 7.5--8.5. Quantitative relative binding potencies of several agonists and antagonists are given. These potencies closely parallel their biological potencies, but all antagonists have higher absolute binding affinities when compared to their potencies to inhibit GnRH-mediated LH secretion in vitro.

Binding, Competitive↗
PubMed1997

Establishment of a novel radioligand assay using eukaryotically expressed cytochrome P4502D6 for the measurement of liver kidney microsomal type 1 antibody in patients with autoimmune hepatitis and hepatitis C virus infection.

BACKGROUND/AIMS: Liver kidney microsomal type 1 antibody (LKM1) is the diagnostic marker of autoimmune hepatitis (AIH) type 2 and is also found in patients with hepatitis C virus (HCV) infection. Cytochrome P4502D6 (CYP2D6) is the documented target antigen of LKM1 in AIH, but not in HCV infection. To compare the reactivity in the two conditions, we established a radioligand assay using eukaryotically expressed CYP2D6 as target. METHODS: A 1.2-kb human CYP2D6 cDNA was isolated from a human liver cDNA library and subcloned into an in vitro transcription vector pSP64 Poly(A). Recombinant CYP2D6 was then produced by in vitro transcription/translation, metabolically labelled with 35S methionine and used in the immunoprecipitation assay. Antibodies that bound radiolabelled CYP2D6 were immunoprecipitated and their levels assessed as cpm. Sera from 50 LKM1-positive patients (26 with AIH; 24 with HCV infection), 128 LKM1-negative patients and 57 normal controls were tested. RESULTS: Reactivity to 35S labelled CYP2D6 was observed in all LKM1-positive sera from patients with AIH and HCV infection, but in none of the controls. The cpm in both conditions were significantly higher than in normal controls (p<0.0001), and were correlated with the immunofluorescence titres of LKM1 (r 0.87, p<0.001 and r=0.64, p<0.001 for AIH and HCV infection, respectively). Reactivity to 35S labelled CYP2D6 was inhibited by addition of an excess of eukaryotically expressed CYP2D6. CONCLUSIONS: CYP2D6 is a major target antigen of both AIH and HCV infection. The novel radioligand assay is highly sensitive and specific.

Adolescent↗
PubMed1987

Biotin radioligand assay with an 125I-labeled biotin derivative, avidin, and avidin double-antibody reagents.

We describe a new radioligand assay for determining biotin in biological fluids by using a mixture of N-[beta-(4-OH-3-125I-phenyl)ethyl]- and N-[beta-(4-OH-3,5-di-125I-phenyl)ethyl]biotinamides as radiotracer, avidin as a binding protein, and an avidin double-antibody as a separation reagent. The radiotracer is synthesized by coupling (at pH 8.5, 20-22 degrees C, 90 min) N-hydroxysuccinimidobiotin to radioiodinated tyramine. The assay curve is linear and the assay itself is sensitive (less than 10 ng/L), reproducible (intra- and interassay CVs 4.1% and 7.0%, respectively), and allows the simultaneous handling of more than 100 samples in less than 4 h. Serum samples from apparently normal subjects contained 100-840 ng of biotin per liter (mean 340 ng/L). Pregnant women had low concentrations of biotin (100-300 ng/L) in their serum. Patients undergoing chronic hemodialysis treatment showed high concentrations (0.5-3.0 micrograms/L), which may be ascribable to the inability of avidin, which was used as the assay binding protein, to distinguish biotin from biotinyl derivatives with an intact ureido ring.

Antibodies↗
PubMed1988

Monoclonal antibodies for progesterone receptor assays and polymorphism studies in breast cancer. Comparison with radioligand assays.

Progesterone receptors (PR) from human breast tumors were assayed by a new method using monoclonal antibodies immobilized on beads (PR-EIA, Abbott Laboratories). EIA results were compared to those obtained with the dextran-coated charcoal method using a tritiated ligand (ORG 2058). The precision and reproducibility of the EIA method were studied over a 3-month period: intra-assay coefficients of variation were less than 6% for the range of the assay (between 5-250 fmol/ml), and inter-assay coefficients of variation calculated on 13 consecutive standard curves were less than 10%, except for standard 0 (33%). PR assays performed on 78 tumors both by EIA and radioligand (RLA) were compared. The linear regression obtained was: PR-EIA = 0.81 RLA+1 fmol/mg protein (r = 0.88). For reproducibility studies, cytosols were assayed twice during a period ranging from 1 week-3 months, both by EIA and RLA. The linear regression obtained between the second assay (B) and the first assay (A) was: B = 0.98 A + 11 fmol/mg protein for RLA (r = 0.98), and B = 0.99 A-7 fmol/mg protein for EIA (r = 0.98). To study the effect of KCl on PR-EIA, 26 tumors were homogenized in 0.4 M KCl Tris buffer and assayed both by EIA and RLA. A good correlation was obtained between the 2 methods, but higher values were obtained with PR-EIA (P = 1.6) in comparison with RLA. The addition of KCl to the cytosol showed that KCl had no effect on EIA results, but significantly lowered RLA results. To study the effect of KCl on progesterone receptor isoforms, cytosols were analyzed by chromatography on TSK G3000 SW columns, and the presence of PR was detected in each fraction by both EIA and RLA. In the absence of KCl, only the oligomeric form of PR was observed; however with both techniques, detection of this form different from tumor to tumor, emphasizing the inter-tumoral molecular heterogeneity of PR. After PR isoform dissociation by KCl (0.4 M) and chromatographic analysis of the forms obtained, monoclonal antibodies detected PR molecular forms different from those observed by radioligand; furthermore, chromatographic patterns obtained were different from one tumor to another and confirmed the inter-tumoral molecular heterogeneity of the progesterone receptor.

Antibodies, Monoclonal↗
PubMed1994

Detection of GAD65 antibodies in diabetes and other autoimmune diseases using a simple radioligand assay.

Autoantibodies to glutamic acid decarboxylase (GAD) are frequent at or before the onset of insulin-dependent diabetes mellitus (IDDM). We have developed a simple, reproducible, and quantitative immunoprecipitation radioligand assay using as antigen in vitro transcribed and translated [35S]methionine-labeled human islet GAD65. By using this assay, 77% (77 of 100) of serum samples from recent-onset IDDM patients were positive for GAD65 antibodies compared with 4% (4 of 100) of serum samples from healthy control subjects. In competition analysis with unlabeled purified recombinant human islet GAD65, binding to tracer was inhibited in 74% (74 of 100) of the GAD65-positive IDDM serum samples compared with 2% of the control samples. The levels of GAD antibodies expressed as an index value relative to a standard serum, analyzed with or without competition, were almost identical (r = 0.991). The intra- and interassay variations of a positive control serum sample were 2.9 and 7.6%, respectively (n = 4). The frequency of GAD antibodies was significantly higher with IDDM onset before the age of 30 (80%, 59 of 74) than after the age of 30 (48%, 10 of 21) (P < 0.01). The prevalence of islet cell antibodies showed a similar pattern relative to age at onset. Because simultaneous occurrences of multiple autoimmune phenomena are common, we analyzed sera from patients with other autoimmune diseases. The frequency of GAD antibodies in sera positive for DNA autoantibodies (8% [2 of 25] and 4% [1 of 25] in competition analysis) or rheuma factor autoantibodies [12% (4 of 35) and 3% (1 of 35) in competition analysis] was not different from that in control samples. In contrast, in sera positive for ribonucleoprotein antibodies the frequency of GAD antibodies was significantly increased (73% [51 of 70] and 10% [7 of 70] in competition analysis [P < 0.025]). In conclusion, even large numbers of serum samples can now be tested for GAD65 antibodies in a relatively short time, allowing screening of individuals without a family history of IDDM for the presence of this marker.

Adolescent↗
PubMed1988

Failure of acid-ethanol treatment to prevent interference by binding proteins in radioligand assays for the insulin-like growth factors.

Acid-ethanol precipitation and gel filtration at acidic pH have been widely used to extract circulating binding proteins for insulin-like growth factor (IGF-I and IGF-II) from plasma or serum samples before radioligand assay for the respective IGFs. Gel filtration on Sephadex G-50 at neutral pH of neutralized acid-ethanol extracts of fetal and adult ovine plasma which had been incubated with 125I-labelled IGF-I or 125I-labelled IGF-II revealed that significant amounts of the IGF-binding protein activity survived the acid-ethanol extraction procedure. Radioimmunoassay for IGF-I in acid-ethanol extracts of plasma samples from fetal, neonatal and adult sheep yielded results which depended upon the method used for separation of the antibody-bound IGF-I tracer from the free IGF-I tracer. Acid gel filtration of ovine fetal and adult plasma was found to remove completely the IGF-binding protein activity. Radioimmunoassay for IGF-I in samples of fetal, neonatal and adult sheep plasma that had undergone acid gel chromatography yielded consistent results for both methods that were used to separate antibody-bound IGF-I tracer from the free tracer. Radioreceptor assays for IGF-II were similarly highly perturbed by the presence of binding protein in acid-ethanol extracts of ovine fetal and adult plasma. We conclude that acid-ethanol extraction can not be used reliably for the removal of IGF-binding proteins, and that only acid gel filtration is a completely safe and valid method.

Acids↗
PubMed2000

Quantitative radioligand assays using de novo-synthesized recombinant autoantigens in connective tissue diseases: new tools to approach the pathogenic significance of anti-RNP antibodies in rheumatic diseases.

OBJECTIVE: To describe new assays for the detection and quantification of antibodies to RNPs in rheumatic diseases, using soluble nuclear antigens synthesized de novo in reticulocyte lysates. METHODS: Sera from 381 patients with various rheumatic diseases, including 212 patients with systemic lupus erythematosus (SLE), were analyzed in order to evaluate the sensitivity and specificity of serum autoantibody reactivities to several recombinant soluble autoantigens: U1-A RNP, Sm-B, SSA/Ro 52 and SSA/Ro 60, SSB/La, and Ku. Radioligand assays (RLAs) were performed following the in vitro transcription and translation of each autoantigen from the corresponding complementary DNA, labeled with 35S-methionine. The radiolabeled protein was then bound by the specific serum autoantibody, forming immune complexes that were captured by protein A-Sepharose beads and quantified by counting the radioactivity. RESULTS: Among the SLE patients, 44% were positive for anti-U1-A RNP activity, 34% for anti-Sm-B, 44% for anti-SSA (32% for Ro 52 and 46% for Ro 60), 32% for anti-SSB/La, and 11% for anti-Ku reactivities. SSA antibodies had a high frequency in patients with mixed connective tissue disease (MCTD) (80%); 65% of these patient sera reacted with Ro 52, 45% with Ro 60, and 45% with U1-A RNP. Twenty percent of the MCTD patients also exhibited antibodies to Sm-B and Ku. In patients with Sjögren's syndrome, anti-SSA was the main anti-RNP antibody (63%), together with SSB/La antibodies (44%). Among patients with inflammatory myopathy, only antibodies against Ro 52 (36%) and Ro 60 (36%) were present. These new RLA allowed observation of a strong correlation (P < 0.0001) between Sm-B antibody levels and the severity of SLE (as measured by the SLE Disease Activity Index), and establishment of a correlation between anti-U1-A RNP antibodies and the occurrence of SLE nephritis (P < 0.02). All RLAs were highly specific for the antigen tested and displayed, in the disease groups studied, a higher sensitivity than conventional immunodiffusion assays. CONCLUSION: These highly sensitive, specific, and quantitative RLAs represent new tools for the detection of autoantibodies to RNP antigens in rheumatic diseases, and may be useful for (differential) diagnosis in clinical practice.

Autoantibodies↗