Immunogenetic aspects of transplantation in the rat brain.

The nature of the brain as an immunologically privileged site is controversial. Using congenic rats, we have demonstrated that grafts that differ from the recipient in the A locus of the MHC produce sensitization following intracerebral transplantation, thus indicating that the brain is not immunologically privileged. The IC grafts show histologic signs of rejection, which are delayed compared with the changes found in the subsequent orthotopic grafts, suggesting that the immune response is weaker in the brain.