A preliminary observation on the immunoisolation effect of the microencapsulated SD rat islet grafts by barium-alginate membrane

To investigate the mechanism of immunoisolation effect of the implanted barium alginate microencapsules containing SD rat islet grafts for the treatment of type 1 diabetes mellitus, the STZ-diabetic Wistar rats were transplanted intraperitoneally with the microencapsulated SD rat islet grafts or under the capsule of kidney with the free islet grafts. Mixed islet-lymphocyte co-cultivation and the determination of the IL-2 and IFN-γ contents in the culture supernatants by ELISA were used to evaluate the responses of the T lymphocytes in the spleen of the tansplanted rats to the allogeneic islets. The experimental results showed that the survival time of the microencapsulated islet grafts was more than 6 weeks, while that of the non-encapsulated islet grafts was (6.6±2.07) days. There was no significant difference in the stimulation indices(SI) between the microencapsulated group and the normal control group, but the SI and the activities of IL-2 and IFN-γ of the free islet graft group were significantly higher than those of the normal control group. Therefore, it was proved that the barium alginate membrane-microencapsulated islet grafts could prolong the survival times for the allogeneic islet grafts and express the hypoimmnoreactivity as demonstrated by the mixed islet-lymphocyte co-cultivation system, thus processing a better immunoisolation effect.