Complex sentence: ATA can be classified according to 2 different schemes: transglutaminase isoform and immunoglobulin reactivity subclass (IgA, IgG) toward transglutaminases.
Split into simpler sentences: ATA can be classified according to 2 different schemes. Transglutaminase isoform and the reactivity of immunoglobulin subclass (IgA, IgG) toward transglutaminases.