CRYPTIC ANTIGENIC DETERMINANTS ON THE EXTRACELLULAR PYRUVATE-DEHYDROGENASE COMPLEX MIMEOTOPE FOUND IN PRIMARY BILIARY-CIRRHOSIS - A PROBE BY AFFINITY MASS-SPECTROMETRY

Affinity mass spectrometry (AMS) was used to evaluate the structural d iversity of the E2 component of pyruvate dehydrogenase complex (PDC) i n normal and diseased liver cells, including those from patients with the autoimmune disease primary biliary cirrhosis (PBC). Two different antibodies to PDC-E2, the immunodominant mitochondrial autoantigen in patients with PBC, were used. AMS was performed directly on frozen liv er sections and purified bile duct epithelial cells. Mass spectrometri c signals associated with the molecular recognition of PBC-specific an tigenic determinants were enhanced by an in situ enzyme-linked signal amplification process. Samples from patients with PBC gave strong posi tive signals for the antigen(s) recognized by the monoclonal antibody C355.1. Conversely, tissues from normal and disease controls showed on ly a minimal signal. AMS was used to identify specific antigenic deter minants within the E2 component of PDC for comparison with unknown ant igenic determinants observed by affinity capture with C355.1 monoclona l antibody from PBC samples. PDC components bound to C355.1 were mappe d and identified by mass before dissociation from the E2 component. A similar approach was used to identify unknown antigenic determinants a ssociated with PBC. We believe AMS may be an important new approach wi th wide application to the identification of molecules associated with a number of disease states.