IMMUNOLOGY

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Novel Antibody Associated with Autoimmune Pancreatitis

Autoimmune pancreatitis is characterized by an inflammatory process that leads to organ dysfunction. The cause of the disease is unknown, and while its autoimmune origin has been suggested it has never been proved. In addition, little is known about the pathogenesis of this condition. As a result, a study published in the New England Journal of Medicine (2009;361:2135-2142), was performed to identify pathogenetically relevant autoantigen targets from a random peptide library with pooled IgG obtained from 20 patients with autoimmune pancreatitis. Results showed that peptide-specific antibodies were detected in serum specimens obtained from the patients. Among the detected peptides, peptide AIP1-7 was recognized by the serum specimens from 18 of 20 patients with autoimmune pancreatitis and by serum specimens from 4 of 40 patients with pancreatic cancer, but not by serum specimens from healthy controls. The peptide showed homology with an amino acid sequence of plasminogen-binding protein (PBP) of Helicobacter pylori and with ubiquitin-protein ligase E3 component n-recognin 2 (UBR2), an enzyme highly expressed in acinar cells of the pancreas. Antibodies against the PBP peptide were detected in 19 of 20 patients with autoimmune pancreatitis (95%) and in 4 of 40 patients with pancreatic cancer (10%). Such reactivity was not detected in patients with alcohol-induced chronic pancreatitis or intraductal papillary mucinous neoplasm. The results were validated in another series of patients with autoimmune pancreatitis or pancreatic cancer: 14 of 15 patients with autoimmune pancreatitis (93%) and 1 of 70 patients with pancreatic cancer (1%) had a positive test for anti-PBP peptide antibodies. When the training and validation groups were combined, the test was positive in 33 of 35 patients with autoimmune pancreatitis (94%) and in 5 of 110 patients with pancreatic cancer (5%).

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