Background/Purpose: The dysregulation of innate immunity contribute to pathogeneses of dermtomyositis (DM). Previous study indicated that high expression of retinoic acid-inducible gene-I (RIG-I) in skeletal muscle tissue participated the mechanism of muscle damage. The aim of the study was to determine gene and protein expression of RIG-I in peripheral CD3+T lymphocytes of DM patient and to evaluate the correlation between the RIG-I in T lymphocyte and clinical characteristics.

Methods:   The study population included 26 treatment-naive DM patients from Department of Rheumatology at China-Japan Friendship Hospital between July 2015 and February 2016 who fulfilled the criteria of definitive DM proposed by Bohan and Peter. All patients did not have indication of clinical symptom, laboratory and auxiliary examinations of virus infection. 14 age-and sex-matched healthy controls were enrolled. The gene and protein expression of RIG-I in peripheral T lymphocytes were determined by RT-PCR and Western blot. Clinical characteristics such as rash, muscle strength, interstitial lung disease (ILD), esophageal involvement and laboratory examination were recorded. Muscle strength and severity of rash were measured by using the Manual Muscle Test (MMT8) and the modified Cutaneous Dermatomyositis Disease Area and Severity Index (CDASI). 8 patients were followed up after 6 months therapy with glucocorticoid accompanies with immunosuppressor or not. T-test were used to compare the differences between groups and Spearman’s rank was applied to investigate the correlation between the RIG-I expression level and clinical characteristics.

Results: Patients were composed of 9 males and 17 females whose average disease duration was 7.69± 6.39 months. 17 patients and 5 patients were complicated with ILD and esophageal involvement respectively. The average MMT8 score and CDASI were 72.15±6.72 and 19.96 ±10.96 respectively. DM patients had significantly higher level of RIG-I both in gene (0.091 ± 0.051 vs 0.052 ± 0.024; p=0.011) and protein (0.30 ± 0.18 vs 0.18 ± 0.08; p=0.005) expression in T lymphocytes than did healthy control subjects. The levels of protein expression were significantly decreased after therapy with 6 months follow-up (0.32 ± 0.16 vs 0.23 ± 0.17; p=0.017). The gene expression level of RIG-I correlated positively with CDASI score (r=0.455, p=0.02) and negatively with T lymphocyte count (r=-0.466, p=0.016). However, RIG-I level showed no correlation with serum Creatine Kinase (CK) level (p=0.356) and MMT8 score (p=0.284). Patients with ILD had higher gene expression level of RIG-I than that without lung disease involvement (0.107 ± 0.493 vs 0.501 ± 0.029; p=0.006). There was no significant difference between patients with esophageal involvement or not (0.084 ± .0.042 vs 0.093 ± 0.054; p=0.747).

Conclusion: The RIG-I expression level increased significantly in peripheral CD3+T lymphocytes of DM patient and descended after treatment. The increased RIG-I level in T lymphocytes were displaying significant association with rash severity and peripheral lymphopenia. Patients with ILD were more likely to have high level of RIG-I in peripheral T lymphocyte.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/retinoic-acid-inducible-gene-i-increased-in-peripheral-cd3t-lymphocytes-of-patients-with-dermatomyositis/