Establishment of an ELISA to detect anti-glycyl-tRNA synthetase antibody (anti-EJ), a serological marker of dermatomyositis/polymyositis and interstitial lung disease

Background: The aminoacyl transfer RNA synthetases (ARSs) are a group of enzymes that charge amino acids to the cognate transfer RNA during the translation process. Previous reports demonstrated autoantibodies to 8 different ARS. Although anti-glycyl-tRNA synthetase antibodies (anti-EJ) are mainly found in patients with inflammatory myopathy, information on their clinical significances is limited, partly due to a lack of commercially available tests. Methods: We developed an ELISA and immunoprecipitation method by using recombinant EJ protein to detect the anti-EJ of 453 patients with various autoimmune connective tissue diseases (ACTDs). We also studied the influence of 3 cytokines-IL-1β, IFN-γ and IFN-α-on the level of EJ mRNA and protein expressed by human fetal lung fibroblasts. Results: Five patients were positive for anti-EJ. Although 3 of these patients had dermatomyositis/polymyositis, the other 2 patients did not have myositis. The three patients with high levels of anti-EJ antibodies in ELISA were complicated with interstitial lung disease. There was no significant change in the level of EJ protein expressed by human fetal lung fibroblasts stimulated by the cytokines. Conclusion: We developed an ELISA to detect anti-EJ by using recombinant protein. This easy-to-use ELISA could help clarify the clinical significance of anti-EJ in ACTDs.