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

Expression of Gal alpha(1-3)Gal on endothelium has been implicated in the r ejection of porcine xenografts. The aim of this study was to determine whet her expression of Gal alpha(1-3)Gal on pig islets varies between pigs aged 5, 12 and 24 weeks, and to investigate whether it is expressed on islets is olated by collagenase digestion or islets maintained in tissue culture. Sam ples of pancreas were obtained from pigs aged 5, 12 and 24 weeks. Islets we re isolated by manual collagenase digestion and density gradient separation . Samples were taken immediately after isolation or after maintenance in ti ssue culture. Pancreas and islet samples were processed, sectioned and stai ned with the lectin BS1-B-4 (which binds to Gal alpha(1-3)Gal residues), an d anti-insulin antibody using a double staining technique. There was no sig nificant difference in the staining patterns to sections of pancreas obtain ed from 5, 12 and 24 week old pigs. Vascular endothelium, connective tissue and the luminal surface of duct epithelial cells stained with BS1-B-4 in a ll sections; endocrine and exocrine cells did not stain. Preliminary experi ments showed that lectin staining to isolated islets was inconsistent betwe en preparations, but expression did not appear to differ significantly betw een ages: lectin staining of some beta-cells was evident in the majority of freshly isolated preparations, but was not detectable on beta-cells follow ing tissue culture. In conclusion, expression of Gal alpha(1-3)Gal did not differ significantly in pancreata from 5, 12 and 24 week old pigs. Prelimin ary experiments showed that Gal alpha(1-3)Gal was expressed by beta-cells i mmediately following isolation, but not after maintenance in culture.