Region-specific Antibodies to Chromogranin B Display Various Immunostaining Patterns in Human Endocrine PancreasGuida Maria PortelaGomesa,c and Mats Stridsbergba Department of Genetics and Pathology, Unit of Pathology, University of Lisbon, Lisbon, Portugal b Department of Medical Sciences, Clinical Chemistry, University of Lisbon, Lisbon, Portugal c University Hospital, Uppsala, Sweden, and the Centres of Gastroenterology and of Nutrition, University of Lisbon, Lisbon, Portugal Correspondence to: Guida Maria PortelaGomes, Dept. of Genetics and Pathology, Unit of Pathology, University Hospital, 75185 Uppsala, Sweden. E-mail: portela_gomes@yahoo.com Chromogranin (Cg) B is an acidic glycoprotein present in neuroendocrine tissue. The sequence shows several dibasic amino acid positions susceptible to proteolytic cleavage. The purpose of this study was to elucidate the expression of CgB epitopes in the human endocrine pancreas. Tissue sections of six human pancreata were immunostained with 16 different region-specific antibodies to the CgB molecule, using double immunofluorescence techniques. The CgB epitope pattern varied in the four major islet cell types. B (insulin)-cells expressed immunoreactivity to all region-specific antibodies. The antibodies to the N-terminal and mid-portions of CgB showed moderate immunoreactivity, the C-terminal antibodies weak. A (glucagon)-cells were reactive only to the N-terminal and mid-portion antibodies but, after microwave pretreatment, to all antibodies, whereas D (somatostatin)-cells expressed only the sequence CgB 244255 and a subpopulation CgB 580595. PP (pancreatic polypeptide) cells were immunostained with antibodies between CgB 1417 and a few with CgB 580593. The fragment CgB 244255 was expressed in all four cell types. The cause of these differences may be cell-specific cleavage or masking of the molecule, but varying translation of CgB mRNA is also possible. The extent to which these epitopes reflect fragments having biological functions remains to be evaluated. (J Histochem Cytochem 50:10231030, 2002) Key Words: chromogranin B, chromogranin B fragments, immunohistochemistry, pancreas, human
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