Immunological reactions following intracerebroventricular transplantation of adrenal medulla

Immunological reactions after intracerebroventricular syn-, allo- and xenogenic transplantation of adrenal medulla were investigated histologically. In xenografts only, T cell infiltration and graft rejection were observed. Syngrafts and allografts were not rejected and were not infiltrated by T cells, although expression of MHC class II antigen was observed at all survival times. Major histocompatibility complex (MHC) class I immunoreactivity was strongly expressed in adrenal cortex syngrafts, which could play a role in the rejection of grafts containing mixed cell populations. The survival of chromaffin cells in allografts was decreased as compared to syngrafts, and there were fewer allograft animals with large numbers of surviving chromaffin cells. There was some increased cellularity (microglia and macrophages) in allografts even though no T cell infiltration was found. Therefore, it appears that this limited survival of intracerebral adrenal medulla allografts is not due to T cell-mediated graft rejection.