Autoantibodies by immunoprecipitation and CPK levels in Mexican patients with PM/DM. A. Immunoprecipitation using sera from Mexican patients with PM/DM. 35S-methionine labeled K562 cell extract was immunoprecipitated using sera from PM/DM patients. Molecular weight markers and positions of Mi-2, TIF-1β, Su and p155/140 (arrowheads) are indicated. B. CPK levels at initial visit are significantly higher in anti-Mi-2 (+) than anti-Mi-2 (-) DM patients. CPK levels of DM patients at initial visit are plotted. Lines in each group indicate median + interquartile range. P = 0.0003 by Mann-Whitney. C. CPK levels at initial and last visit in each DM patient compared between anti-Mi-2 (+) and (-) groups. Top, anti-Mi-2 (+) group, initial versus last visit, P < 0.0001 by Wilcoxon matched pairs test. CPK, creatine phosphokinase; PM/DM, polymyositis/dermatomyositis.