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Autoantibodies to a 140-kd protein in juvenile dermatomyositis are associated with calcinosis
H Gunawardena1, L R Wedderburn, H Chinoy
1Royal National Hospital for Rheumatic Diseases, and University of Bath, Bath, UK.
Insights
Researchers identified anti-p140 autoantibodies in juvenile dermatomyositis (DM) patients, finding a significant association with calcinosis. This discovery may define a distinct clinical and immunogenetic phenotype within juvenile myositis.
Area of Science:
- Pediatric Rheumatology
- Immunology
- Autoantibody Research
Background:
- Juvenile dermatomyositis (DM) is a rare autoimmune disease affecting children.
- Identifying novel autoantibodies is crucial for understanding disease mechanisms and clinical outcomes in juvenile DM.
- Previous research has identified various autoantibodies associated with juvenile DM, but further characterization is needed.
Purpose of the Study:
- To investigate the presence and significance of autoantibodies targeting a 140-kd protein (p140) in children with juvenile myositis.
- To determine the clinical and immunogenetic associations of anti-p140 autoantibodies in this cohort.
Main Methods:
- Sera and clinical data were collected from children enrolled in the Juvenile DM National Registry and Repository.
- Immunoprecipitation and immunodepletion techniques were used to identify and characterize the p140 autoantigen.
- HLA class II haplotype associations were analyzed using DNA samples and compared to control subjects.
Main Results:
- Anti-p140 autoantibodies were detected in 23% of juvenile myositis patients, exclusively in those with juvenile DM.
- The p140 autoantigen was identified as NXP-2.
- Anti-p140 positivity was significantly associated with calcinosis (OR 7.0, P < 0.005) and distinct clinical features compared to anti-p155/140 antibodies.
- HLA-DRB1*08 was a potential risk factor for anti-p140 autoantibody positivity.
Conclusions:
- Anti-p140 autoantibodies represent a significant subset of autoantibodies in juvenile DM.
- The presence of anti-p140 autoantibodies may indicate a specific immunogenetic and clinical phenotype, including a higher risk of calcinosis.
- This finding contributes to a better understanding of the heterogeneity within juvenile myositis.
Objective:
The identification of novel autoantibodies in juvenile dermatomyositis (DM) may have etiologic and clinical implications. The aim of this study was to describe autoantibodies to a 140-kd protein in children recruited to the Juvenile DM National Registry and Repository for UK and Ireland.
Methods:
Clinical data and sera were collected from children with juvenile myositis. Sera that recognized a 140-kd protein by immunoprecipitation were identified. The identity of the p140 autoantigen was investigated by immunoprecipitation/immunodepletion, using commercial monoclonal antibodies to NXP-2, reference anti-p140, and anti-p155/140, the other autoantibody recently described in juvenile DM. DNA samples from 100 Caucasian children with myositis were genotyped for HLA class II haplotype associations and compared with those from 864 randomly selected UK Caucasian control subjects.
Results:
Sera from 37 (23%) of 162 patients with juvenile myositis were positive for anti-p140 autoantibodies, which were detected exclusively in patients with juvenile DM and not in patients with juvenile DM-overlap syndrome or control subjects. No anti-p140 antibody-positive patients were positive for other recognized autoantibodies. Immunodepletion suggested that the identity of p140 was consistent with NXP-2 (the previously identified MJ autoantigen). In children with anti-p140 antibodies, the association with calcinosis was significant compared with the rest of the cohort (corrected P < 0.005, odds ratio 7.0, 95% confidence interval 3.0-16.1). The clinical features of patients with anti-p140 autoantibodies were different from those of children with anti-p155/140 autoantibodies. The presence of HLA-DRB1*08 was a possible risk factor for anti-p140 autoantibody positivity.
Conclusion:
This study has established that anti-p140 autoantibodies represent a major autoantibody subset in juvenile DM. This specificity may identify a further immunogenetic and clinical phenotype within the juvenile myositis spectrum that includes an association with calcinosis.
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