Clinical and Serologic Characterization of an Argentine Pediatric Myositis Cohort: Identification of a Novel Autoantibody (anti-MJ) to a 142-kDa Protein

Seven patients immunoprecipitated proteins of apparent molecular weight 142 kDa from ³⁵S methionine-labeled K562 whole-cell extract, separated on an 8% SDS polyacrylamide 20-cm gel (data not shown). Immunoprecipitation was repeated for these 7 patients and the proteins electrophoretically resolved on a 5% SDS polyacrylamide minigel, enhanced with sodium salicylate and visualized by autoradiography (shown here). Lanes 1–6 represent patients included as “MJ” in Table 2; Lane 7, a patient included as “p155/140” in Table 2. Also shown is a ¹⁴C molecular weight marker (Mr).