Ultrastructural identification of cells expressing Galα1-3Gal antigen in cultured fetal porcine isletlike cell clusters

Ultrastructural Identification of Cells Expressing Gal␣1-3Gal Antigen in Cultured Fetal Porcine Isletlike Cell Clusters V. Strokan, W. Bennet, J. Mo¨lne, O. Korsgren, and M.E. Breimer

T

HE distribution of Gal␣1-3Gal antigen (␣-Gal) in cultured fetal porcine isletlike cell clusters (ICC) is unclear. Previous light microscopic studies indicated an increased expression of Gal␣ in cultured fetal ICC but did not exactly define which cells expressed the antigen.1 Diabetic patients transplanted with ICC developed increased anti-Gal␣ titers after xenotransplantation.2,3 This article describes the ultrastructural distribution of the Gal␣ antigen in cultured fetal porcine ICCs. MATERIALS AND METHODS ICCs (n ⫽ 3) were obtained from Swedish landrace sows at 70 ⫾ 5 days of gestation and cultured for 5 days.4 The samples were fixed and processed for immunoelectron microscopy (IEM) and for transmission electron microscopy (TEM).5 Single and doubleimmunogold labelings were performed in different combinations using Griffonia simplicifolia isolectin B4 (GS-lectin), human affinity-isolated anti-Gal␣1-3Gal antibody (anti-Gal), and antibodies against pancreatic hormones, von Willebrand factor, and vimentin. Controls comprised light microscopical immunostaining of paraffin-embedded porcine pancreatic tissues as well as TEM and IEM studies of adult porcine islet cells (API).6

RESULTS

The ␣-Gal antigen was intensely expressed by endothelial cells (EC), duct epithelial cells, acinar cells, and occasional white blood cells. A small portion of immature endocrine cells reacted weakly with GS-lectin and human anti-Gal. In addition, strong ␣-Gal reactivity was observed on flattened cells that covered the ICC surfaces. TEM analysis revealed that these cells had specific epithelial-type features. In contrast to EC, these cells were nonreactive with antivimentin antibody. Thus, IEM and TEM analysis allowed us to identify them as centroacinar cells (CAC) originating from intraislet pancreatic ducts.

© 2000 by Elsevier Science Inc. 655 Avenue of the Americas, New York, NY 10010 Transplantation Proceedings, 32, 1063 (2000)

CONCLUSIONS

Cultured porcine fetal endocrine cells are devoid of the ␣-Gal antigen similar to API cells. However, some immature endocrine cells showed weak ␣-Gal reactivity. An intense expression of the ␣-Gal antigen by CAC was found. In many clusters, these cells covered the entire ICC surfaces, thus exposing ␣-Gal epitopes to the outside. In case of xenotransplantation to humans, these epitopes will be likely targets for human xenoreactive antibodies. It remains unclear if this will mediate damage to the endocrine cells.

REFERENCES 1. McKenzie IFC, Koulmanda M, Mandel TE, et al: Xenotransplantation 2:1, 1995 2. Satake M, Kawagishi N, Rydberg L, et al: Xenotransplantation 1:89, 1994 3. Galili U, Tibell A, Samuelsson B, et al: Transplantation 59:1549, 1995 4. Korsgren O, Sandler S, Landstro ¨m AS, et al: Transplantation 45:509, 1988 5. Strokan V, Mo ¨lne J, Svalander CT, et al: Transplantation 66:1495, 1998 6. Strokan V, Bennet W, Korsgren O, et al: Abstract book, 9th Congress of the European Society for Organs Transplantation, 1999 (Abstract 1275)

From Sahlgrenska University Hospital (V.S., J.M., M.E.B.), Go¨teborg, Huddinge Hospital (W.B.), Huddinge, and Uppsala University (O.K.), Uppsala, Sweden. Address reprint requests to Dr V. Strokan, Sahlgrenska University Hospital, Department of Pathology, 413 45 Goteborg, Sweden.

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