Anti-KJ: a new antibody associated with the syndrome of polymyositis and interstitial lung disease.

Antibodies to aminoacyl-tRNA synthetases (anti-Jo-1, anti-PL-7, anti-PL-12) have been found in the serum of some patients with polymyositis (PM). Patients with these antibodies have an unusually high rate of interstitial lung disease (ILD) in association with their PM. Two patients (K.J. and B.T.) with severe ILD and PM were found to have antibodies to a cytoplasmic antigen, but tests to determine whether the antigen was an aminoacyl-tRNA synthetase were negative, including tests of KJ serum for inhibitory effects on the 20 synthetases. KJ immunoprecipitates did not contain tRNA, in contrast to antisynthetase sera. When IgG samples were added to a reticulocyte in vitro translation system at a concentration of 0.3 mg/ml, KJ IgG inhibited globin mRNA translation by 98%, while anti-Jo-1 IgG inhibited 62% and normal IgG had little effect. Thus, both anti-KJ and the antisynthetases are directed at antigens that are involved in translation and protein synthesis, and both are associated with the syndrome of lung disease and PM. This syndrome may be associated with antibodies to translation-related proteins in general, which may have implications for the link of PM and enteroviruses, which are mRNA viruses.