Expression of the GALalpha(1-3)GAL epitope on pig islets

Expression of Galalpha(1-3)Gal on endothelium has been implicated in the rejection of porcine xenografts. The aim of this study was to determine whether expression of Galalpha(1-3)Gal on pig islets varies between pigs aged 5, 12 and 24 weeks, and to investigate whether it is expressed on islets isolated by collagenase digestion or islets maintained in tissue culture. Samples of pancreas were obtained from pigs aged 5, 12 and 24 weeks. Islets were isolated by manual collagenase digestion and density gradient separation. Samples were taken immediately after isolation or after maintenance in tissue culture. Pancreas and islet samples were processed, sectioned and stained with the lectin BS1-B4 (which binds to Galalpha(1-3)Gal residues), and anti-insulin antibody using a double staining technique. There was no significant difference in the staining patterns to sections of pancreas obtained from 5, 12 and 24 week old pigs. Vascular endothelium, connective tissue and the luminal surface of duct epithelial cells stained with BS1-B4 in all sections; endocrine and exocrine cells did not stain. Preliminary experiments showed that lectin staining to isolated islets was inconsistent between preparations, but expression did not appear to differ significantly between ages: lectin staining of some beta-cells was evident in the majority of freshly isolated preparations, but was not detectable on beta-cells following tissue culture. In conclusion, expression of Galalpha(1-3)Gal did not differ significantly in pancreata from 5, 12 and 24 week old pigs. Preliminary experiments showed that Galalpha(1-3)Gal was expressed by beta-cells immediately following isolation, but not after maintenance in culture.