Detection of autoantigens by immunoblotting using a peroxidase-anti-peroxidase complex.

An immunoblotting procedure using a peroxidase-anti-peroxidase (PAP) complex was developed for the detection of autoantigens in crude mixtures by human autoimmune sera. Thymus proteins were transferred to a nitrocellulose sheet after electrophoresis in polyacrylamide gels and probed with a 1:100 dilution of serum. The location and extent of immunoglobulin G (IgG) binding was determined by sequential reaction with: rabbit anti-human IgG, goat anti-rabbit IgG and rabbit peroxidase-anti-peroxidase complex. The peroxidase was allowed to react with chloronaphthol and low levels of autoantigen/autoantibody complex were detectable with virtual absence of background colour. The inclusion of human IgG and its pepsin-generated fragment provided a means of controlling and calibrating the blotting procedure.