Demonstration of autoantibody specificity by inhibition in ELISA.

A: Inhibition of serum IgA reactivity to glycoprotein 2 (GP2). A serum with high anti-GP2 IgA level at a dilution giving an optical density (OD) of 0.8 was pre-incubated with recombinant GP2 (Isoform alpha) and tissue transglutaminase (TG) at decreasing concentrations from 0–10 μg/mL. B: Inhibition of serum IgA reactivity to tTG. A serum with high anti-tTG IgA level at a dilution giving an optical density (OD) of 1.5 was pre-incubated with recombinant GP2 (Isoform alpha) and tTG at decreasing concentrations from 0–10 μg/mL. Data are presented as means of triplicate measurements with the corresponding standard deviation.