Impact of culture and cryopreservation on MHC class II antigen expression in canine and porcine islets

Canine and porcine islets were either cultured for 10 days at 37 °C or cryopreserved. The effect of these treatments on MHC class II antigen expression was examined by indirect immunofluorescence test using the class II monoclonal antibody 2MC3. Within untreated canine islets exclusively round shaped cells as leukocytes and monocyte/macrophage like cells with dendritic branches were positive with 2MC3. Porcine islets additionally exhibited strong immunofluorescence of the vascular endothelium. Tissue culture significantly reduced the class II antigen expression in both species.The majority of the untreated canine islets had between 5 and 19 2MC3 positive cells. Cell culture reduced the number of class II positive cells to a maximum of 3 and even 84.9% of the islets were completely negative for class II antigens. Porcine islets showed a total class II antigen loss of the vascular endothelium, whereas leukocytes and monocytes/macrophages remained class II antigen positive. Cryopreservation did not have clear-cut effects on the MHC expression in both species.