Immunological aspects of neural transplantation

Summary

The mechanisms of the immunological rejection after xenogeneic neural transplantation were investigated. Tissue from a newborn mouse neocortical tissue was grafted into the third ventricle of a 4-week-old rat brain. The first event observed following the transplantation is the inosculation of blood vessels between those originating in the donor tissue and the host tissue. Thereafter, major histocompatibility complex (MHC) antigens were detected on the vascular endothelial cells at day 6, followed by the infiltration of cytotoxic/suppressor T-cells into the grafted tissue from day 8. These results raised the possibility that the expression of MHC antigens on the vascular endothelial cells renders the grafted tissues competent to initiate and participate in the immune reaction. This possibility was further confirmed by the finding that the host peripheral lymphocytes were sensitized by the donor MHC antigens, particularly class II, in the mixed lymphocyte culture experiment. Blood vessels in the grafted tissue are considered to be the initial target of the T-cells, because horseradish peroxidase perfusion experiment clearly demonstrated that the blood-brain barrier was destroyed at the 9th day after the transplantation.