CALRETICULIN - THE POTENTIAL AUTOANTIGEN IN CELIAC-DISEASE

Monoclonal antibodies to gliadin were recently found to cross-react wi th epitopes on rat enterocytes. Two molecules of mel. mass 62 and 66 k Da were isolated from enterocyte lysates by affinity chromatography us ing antigliadin monoclonal antibodies. The N-terminal amino acid seque nce of the 62-kDa protein was determined to be XXXIYFKEQFLD. This amin o acid sequence corresponds to amino acid sequence of rat calreticulin . The presence of calreticulin in enterocyte lysates was further confi rmed using anticalreticulin serum. Anticalreticulin serum was also use d to investigate the reactivity of isolated rat calreticulin. To analy ze whether gliadin and calreticulin share similar epitopes recognized by anticalreticulin antibodies, synthetic dodecapeptides derived from the amino acid sequence of a gliadin were used in competitive ELISA as say. Two gliadin peptides, QEQVPLVQQQQF and YQLLQELCCQHL, were found t o inhibit the binding of rabbit anti-rat calreticulin sera to rat calr eticulin. The significant correlation was detected between IgA antical reticulin and antigliadin antibodies (r = 0.827; P < 0,001) in celiac patients. (C) 1995 Academic Press, Inc.