Using an immunocytochemical method, we examined the immunological responses of adult mice to intracerebellar syngeneic and allogeneic fetal mouse brainstem transplants (embryonic days 12-14). Syngeneic grafts and major histocompatibility complex (MHC)-compatible and non-MHC-incompatible allogeneic grafts survived well, showing no histological signs of rejection even 6 months after transplantation, and with no expression of MHC antigens being observed in any of the grafts. However, most cases of both MHC- and non-MHC-incompatible allografts showed rejection responses, such as marked neovascularization, cellular infiltration and necrosis, two weeks to one month after transplantation. In animals showing rejection, Class I MHC antigens were found on grafted neuronal tissue. An increased number of reactive astrocytes was also observed in the grafts. High levels of Class I antigen expression and prominent gliosis correlated with vigorous cellular infiltration. A quantitative analysis of T cell subsets in the animals showing rejection revealed that the L3T4/Lyt-2 ratio was 1.02±0.21 (mean ± S.D.), indicating that helper/inducer and cytotoxic/suppressor T cells appeared equally in the rejection of MHC- and non-MHC-incompatible allografts. We consider that in these experiments, the brain was not completely an immunologically privileged site, and that MHC- and non-MHC-incompatible intraparenchymal neural transplants were not shielded from host immune surveillance.
- Major histocompatibility complex
- Neural transplantation
- T cell subset
ASJC Scopus subject areas