MX1 and idiopathic pulmonary fibrosis: We have also found that a positive anti-MX1 autoantibody test for at least one of the three subclasses of antibody (immunoglobulin (Ig) G, IgA, and IgM) in serum [9] predicts a good prognosis in patients with non-IPF IIP after adjustment for modified interstitial lung disease (ILD)-gender-age-physiology (GAP) stage [14, 15].