EXPRESSION OF GAL-ALPHA(1,3)GAL ON NEONATAL PORCINE ISLET BETA-CELLS AND SUSCEPTIBILITY TO HUMAN ANTIBODY COMPLEMENT LYSIS/

Neonatal porcine pancreases may be a potential source of islets for tr ansplantation into patients with type 1 diabetes; however, whether the se cellular grafts will be susceptible to damage by human natural anti body-mediated rejection remains controversial. Although me and others have demonstrated that porcine islets bind human IgG and IgM, it remai ns unknown if they express the xenoreactive antigen Gal alpha(1,3)Gal beta(1,4)GlcNAc-R (Gal epitope). In this study, by using the Gal-speci fic lectin IB4 for immunohistochemistry and fluorescence-activated cel l sorter (FACS) analysis, we determined which cell types present in po rcine neonatal islet cell (NIC) aggregates express the Gal epitope and which ones are susceptible to lysis by activation of the human comple ment. After FAGS analysis, 30.0 +/- 3.0% of porcine NICs mere shown to express Gal, whereas 70.0 +/- 2.0% did not. Histological assessment o f Gal-expressing cells revealed that 54.9 +/- 8.8% stained positive fo r either insulin or glucagon. In contrast, 68.8 +/- 8.4% of the Gal-ne gative population stained positive for the pancreatic hormones insulin and glucagon. Incubation of either the Gal-positive or -negative cell s with human AB serum plus complement for 1.5 h resulted in the lysis of >90% of the cells. These results demonstrate that porcine NIC aggre gates are composed of Gal-expressing cells and that expression of Gal is not restricted to nonendocrine cells. Furthermore, both Gal-positiv e and Gal-negative cells are susceptible to human antibody/complement- mediated cytolysis, suggesting that this form of immunological destruc tion is an obstacle that will need to be overcome before porcine NIC a ggregates can be used clinically.