Islet xenotransplantation : An immunological study in the pig-to-mouse model

Abstract: Successful clinical xenotransplantation, i.e., transplantation between species, would eliminate the shortage of donor organs. In order to study the acute cellular rejection reaction following discordant xenogeneic transplantation, an experimental pig-to- mouse islet xenotransplantation model was established. Further, immunological processes were evaluated using genetically deficient (knock-out) recipient mice and pharmacological agents exerting cytokine-modulatory actions.Xenogeneic islet transplantation persists in mice deficient in antibodies, interleukin-6, perforin or granzyme B, suggesting that neither xenoreactive antibodies or interleukin-6 nor granule-mediated lysis are of critical importance to the rejection process. Instead, the immune response following pig-to-mouse islet xenotransplantation bears a close morphological resemblance to a T helper (Th) 1-dependent delayed-type hypersensitivity-reaction with a massive infiltration of macrophages and comparatively small amounts of peripherally accumulated T cells. It may be speculated that islet xenograft destruction is a macrophage-mediated process regulated by T cells. Indeed, Th1-associated cytokines with macrophage-activating properties (interferon-γ and tumor necrosis factor-α) and interleukin-2 seem to be important to islet xenograft rejection, even though other cytokines eventually substitute for the lack of those in a majority of animals.Key words: xenotransplantation, porcine, islet, in vivo, knock-out mouse,immunohistochemistry, CsA, MDL 201,449A, Ig, FcR, IL-6, perforin, granzyme B,macrophage, eosinophilic granulocyte, T cell, TCR, IFN- g, TNF- a, IL-2.

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