Tilapia islets. Brockmann bodies (BBs), transplanted under the kidney capsule (KC) of diabetic nude mice provide long-term normoglycemia, but, when transplanted into euthymic mice, reject in about one week. Objectives: The present study characterizes the cellular infiltrates at several time points during the xenograft rejection process. Methods: Tilapia BBswere harvested, fragmented, cultured overnight, and then transplanted under the KC of streptozotocindiabetic Balb/c mice. Glucose levels were measured daily until the mice were killed at I (n=2), 2 (n=2), 3 (n=3), and 5 days (n=3) post transplantation and at the time of BBgraft rejection (n=6). Serial frozen sections of graft-bearing kidneys were stained for murine macrophages (MOMA-2, F4/S0, M170), CD4+ (L3T4) T-cells (YTS 191.1), and CDS+ (Ly-2) T-cells (YTS 169.4) by indirect immunoperoxidase; the presence of granulocytes and plasma cells was assessed with H&E stained sections. Results: At I day, the grafts have undergone some central necrosis with macrophage infiltration. By 2 days, these changes are very well-developed and granulocytes, almost exclusively eosinophils, begin to surround the graft. At 3 days, rare CD4+ and CDS+ T-cells are seen at the graft kidney interface. Macrophages massively infiltrate the necrotic foci and pepper the graft. At 5 days and at rejection, macrophages and eosinophils predominated in the center of rejecting grafts while CDS+ T-cells and CD4+ T-cells were present at the periphery. Plasma cells were rare. Conclusion: We conclude that cell-mediated processes and eosinophils play roles in the rejection of cellular xenografts across this very wide phylogenetic barrier.

Keywords: Islets, Cell Transplantation, Graft Rejection, macrophage, CDBT-Iymphocyte, discordant, Xenotransplantation