[Autoantibody diagnostics in idiopathic inflammatory myopathy]. / Autoantikörperdiagnostik bei idiopathisch inflammatorischen Myopathien.

Idiopathic inflammatory myopathy (IIM) is a group of rare and heterogeneous systemic diseases that manifest not only in the muscles but also in the skin, joints, and lungs. Initial symptoms can be isolated and variable and thus the diagnosis poses challenges to various specialist groups. As autoantibodies are sometimes the only specific findings that lead to the diagnosis and appropriate treatment, basic knowledge of them is essential. This article explains the available test systems, names the clinical indications necessary for the initiation of autoantibody diagnostics, provides information on the etymology, antigens, synonyms, and first descriptors, describes indirect immunofluorescence on HEp­2 cells induced by myositis antibodies, and provides clinical-serological associations. The comparison of the autoantibody findings with the clinical symptoms and laboratory findings enables the identification of false positive or false negative laboratory findings in the sense of a plausibility check.

Frequency of disease-associated and other nuclear autoantibodies in patients of the German Network for Systemic Scleroderma: correlation with characteristic clinical features.

INTRODUCTION: In the present study, we analysed in detail nuclear autoantibodies and their associations in systemic sclerosis (SSc) patients included in the German Network for Systemic Scleroderma Registry. METHODS: Sera of 863 patients were analysed according to a standardised protocol including immunofluorescence, immunoprecipitation, line immunoassay and immunodiffusion. RESULTS: Antinuclear antibodies (ANA) were detected in 94.2% of patients. In 81.6%, at least one of the autoantibodies highly associated with SSc or with overlap syndromes with scleroderma features was detected, that is, anti-centromere (35.9%) or anti-topoisomerase I (30.1%), followed in markedly lower frequency by antibodies to PM-Scl (4.9%), U1-ribonucleoprotein (U1-RNP) (4.8%), RNA polymerases (RNAPs) (3.8%), fibrillarin (1.4%), Ku (1.2%), aminoacyl-transfer RNA synthetases (0.5%), To (0.2%) and U11-RNP (0.1%). We found that the simultaneous presence of SSc-associated autoantibodies was rare (1.6%). Furthermore, additional autoantibodies were detected in 55.4% of the patients with SSc, of which anti-Ro/anti-La, anti-mitochondrial and anti-p25/p23 antibodies were most frequent. The coexistence of SSc-associated and other autoantibodies was common (43% of patients). SSc-associated autoantibodies disclosed characteristic associations with clinical features of patients, some of which were previously not acknowledged. CONCLUSIONS: This study shows that five autoantigens (that is, centromere, topoisomerase I, PM-Scl, U1-RNP and RNAP) detected more than 95% of the known SSc-associated antibody responses in ANA-positive SSc patients and characterise around 79% of all SSc patients in a central European cohort. These data confirm and extend previous data underlining the central role of the determination of ANAs in defining the diagnosis, subset allocation and prognosis of SSc patients.

Autoantibody detection using indirect immunofluorescence on HEp-2 cells.

The detection of autoantibodies is an important element in the diagnosis and monitoring of disease progression in patients with autoimmune diseases. In laboratory diagnostic tests for connective tissue and autoimmune liver diseases, indirect immunofluorescence on HEp-2 cells plays a central role in a multistage diagnostic process. Despite the high quality of diagnostics, findings at different laboratories can differ considerably due to a lack of standardization, as well as subjective factors. The present paper formulates recommendations for the standardized processing and interpretation of the HEp-2 cell test for the detection of non-organ-specific (especially antinuclear) antibodies. It provides requirements regarding the diagnostic tests used, instructions for laboratory procedure and evaluation, and recommendations for interpretation. For an optimal laboratory diagnostic process, it is useful to have an informative, tentative clinical diagnosis and an experienced laboratory diagnostician. In addition, the following key elements are recommended: initial screening using indirect immunofluorescence on carefully chosen HEp-2 cells beginning with a serum dilution of 1:80 and evaluation under a microscope with powerful illumination; results from a titer of 1:160 upwards being considered positive; internal laboratory quality control; and standardized interpretation. The aim is to improve diagnostic tests and care of patients with autoimmune diseases as a central concern of the European Autoimmunity Standardization Initiative (EASI).

No association between systemic sclerosis and C77G polymorphism in the human PTPRC (CD45) gene.

OBJECTIVE: The functional variant C77G (rs17612648) of PTPRC (CD45) was described to confer risk for systemic sclerosis (SSc) in German Caucasians. We analyzed this association in an independent, larger German cohort. METHODS: We genotyped 171 cases and 179 controls. Cases were subgrouped according to sex, autoantibody profiles, or clinical subsets. RESULTS: No association of SSc with C77G was detected in the whole dataset, in subgroups, or in combined analyses with a previous study. CONCLUSION: The results do not confirm PTPRC C77G as a general and independent risk factor for development of SSc.

Clinical diagnosis compared to classification criteria in in a cohort of 54 patients with systemic sclerosis and associated disorders.

OBJECTIVE: To compare clinical diagnosis with two validated classification criteria for systemic sclerosis (SSc) in a cohort of Swiss patients with SSc and associated disorders. METHODS: Charts of 54 patients with SSc and associated disorders were reviewed and compared with data obtained at a thorough clinical examination using a standardised protocol (Raynaud's phenomen [RP], skin involvement, nailfold capillary microscopy and determination of autoantibody pattern). RESULTS: According to patient records 6 patients had diffuse cutaneous SSc (dcSSc), 23 limited cutaneous SSc (lcSSc) and 20 were not classified. Two patients had mixed connective tissue disease (MCTD) and 3 overlap syndromes. At the time of clinical examination, 7 patients showed dcSSc (6 plus 1 patient originally classified as lcSSc), 26 lcSSc (20 plus 6 originally not classified) and 16 patients had severe RP which was arbitrarily classified as Raynaud's syndrome (RS). 15 of the latter 16 were antinuclear antibody positive and 7 exhibited pathological nailfold capillaries. On the basis of LeRoy and Medsger's criteria, 6 of these patients could be further classified as limited SSc (lSSc). Of 49 sera tested, 14 contained centromere antibodies at clinical examination, 16 Scl-70, 5 RNA-pol, 1 Ku, 12 antibodies with unknown specificity, and one serum was autoantibody negative. CONCLUSIONS: A substantial number of patients with minor cutaneous manifestations do not fulfil ACR classification criteria, though they have typical clinical signs of SSc. Characteristic features in these patients are presence of Raynaud's phenomenon, antinuclear antibodies and pathological changes in nailfold capillary microscopy. Application of the diagnostic criteria recently proposed by LeRoy and Medsger makes it possible to name many of these patients. The use of these criteria is recommended for clinical management.

Diagnosis and prognosis of early rheumatoid arthritis, with special emphasis on laboratory analysis.

Diagnosis of rheumatoid arthritis (RA) is mainly based on clinical criteria of symmetric polyarthritis of the hands and feet, with morning stiffness lasting usually more than 1 h. Autoantibodies typical for RA, i.e., rheumatoid factors and anti-cyclic citrullinated peptide, and measurements of inflammation add more specific information, especially for early diagnosis, where clinical presentation may be oligosymptomatic involving only a few joints. These laboratory parameters are also relevant for prognosis of disease persistence, functional impairment and radiological progression.

Development of a CENP-A/CENP-B-specific immune response in a patient with systemic sclerosis.

Antibodies directed against an epitope motif on CENP-A have been shown to cross-react with mimotopes on other autoantigens and on Epstein-Barr nuclear antigen 1 (EBNA-1), suggesting a molecular mimicry. We describe here the gradual development of an anticentromere immune response in a patient with systemic sclerosis, which started from an antihistone response and was not mediated by molecular mimicry. Via an epitope on histone H3, the antibody response spread to a homologous epitope in the H3 homology domain of CENP-A. This was followed by an intramolecular epitope spreading to N-terminal peptides of CENP-A containing the known epitope motif G-P-X(1)-R-X(2). From there it spread to corresponding epitopes on CENP-B and to mimotopes of the major CENP-A epitope motif on other autoantigens including EBNA-1. Whether the D-penicillamine treatment received by this patient was involved in the triggering of this cascade remains a matter of speculation.

Autoantibodies directed to novel components of the PM/Scl complex, the human exosome.

The autoantigenic polymyositis/scleroderma (PM/Scl) complex was recently shown to be the human homologue of the yeast exosome, which is an RNA-processing complex. Our aim was to assess whether, in addition to targeting the known autoantigens PM/Scl-100 and PM/Scl-75, autoantibodies also target recently identified components of the PM/Scl complex. The prevalence of autoantibodies directed to six novel human exosome components (hRrp4p, hRrp40p, hRrp41p, hRrp42p, hRrp46p, hCsl4p) was determined in sera from patients with idiopathic inflammatory myopathy (n = 48), scleroderma (n = 11), or the PM/Scl overlap syndrome (n = 10). The sera were analyzed by enzyme-linked immunosorbent assays and western blotting using the affinity-purified recombinant proteins. Our results show that each human exosome component is recognized by autoantibodies. The hRrp4p and hRrp42p components were most frequently targeted. The presence of autoantibodies directed to the novel components of the human exosome was correlated with the presence of the anti-PM/Scl-100 autoantibody in the sera of patients with idiopathic inflammatory myopathy (IIM), as was previously found for the anti-PM/Scl-75 autoantibody. Other clear associations between autoantibody activities were not found. These results further support the conception that the autoimmune response may initially be directed to PM/Scl-100, whereas intermolecular epitope spreading may have caused the autoantibody response directed to the associated components.