%0 Journal Article
%T Microencapsulation of Allogeneic Parathyroid Tissue Succeeds by Delaying Immunization of the Host, not by Protecting the Graft Against the Host¡¯s Activated Immune System
%A T. Bohrer
%A K. Stelter
%A I.-S. Steler
%A C. Dietrich
%J Transplantationsmedizin
%D 2006
%I Pabst Science Publishers
%X Background: To examine in an experimental animal study whether alginate microencapsulation of allogeneic parathyroid tissue succeeds by protecting the graft against the host¡¯s activated immune system or by delaying immunization of the host. Methods: Lewis and Dark Agouti rats (n = 200 of each) were used. Parathyroidectomy (PTX) of the hosts was followed by allogeneic transplantation of microencapsulated parathyroid tissue (PT) to the following 3 groups of 5 animals each without immunosuppression: group I, early onset immunoreaction, group II, late onset immunoreaction, and group III, immunization. In group I, an allogeneic skin graft from the same donor was transplanted 3 weeks after microencapsulated PT transplantation and the rejection time determined to assess the host¡¯s immunoreaction. In group II, allogeneic skin graft transplantation was carried out under the identical conditions 8 weeks after microencapsulated PT transplantation. And in group III, allogeneic skin graft transplantation was performed as an immunostimulant 3 weeks before transplantation of microencapsulated PT. Each of the 3 study groups I to III was compared with a corresponding control group I to III receiving native PT allotransplants. Once a week, the titers of cytotoxic antibodies were analyzed and graft function was monitored based on total serum calcium levels [Ca++]. In group IV, 2 allogeneic skin grafts within 2 weeks were given after PTX (study animals), or without prior PTX (controls). Results: Four out of 5 animals in group I, and 3 out of 5 animals in group II lost graft function within 11 weeks after transplantation of microencapsulated PT. In the respective control groups, graft function was lost within 6 weeks. Surprisingly, none of the immunostimulated animals in group III experienced any transplant success, all allogeneic skin grafts being rejected within 11.6 days. There was no significant (p > 0.05) difference in skin graft rejection between study and control groups III. Low cytotoxic antibodies were detected in both study animals and controls of all 4 groups one week after PT allotransplantation (p > 0.05 study and control groups), whereas cytotoxic antibodies were elevated to peak levels in all animals immediately after skin graft transplantation. Conclusion: Earlier successes in microencapsulation technology are not due to the protection offered to the graft by alginate microencapsulation, but rather by the delayed immunization of the host.
%K cytotoxic antibodies
%K graft rejection
%K microencapsulation
%K parathyroid allotransplantation
%U http://www.transplantation.de/fileadmin/transplantation/txmedizin/txmedizin_2006_1/07_bohrer.pdf