Neural tissue xenografting

Neural transplantation may become an important treatment alternative for fo cal brain disorders. To date, the most successful grafts have been obtained in patients with Parkinson's disease. Completely normalized dopamine produ ction and reduction of Parkinsonian symptoms have been demonstrated 10 year s after grafting. However, the allogeneic donor tissue has to be obtained f rom induced abortions, and there are logistical difficulties, risks of infe ction, and ethical constraints limiting a wider clinical use. Xenografting is an alternative that could bridge these limitations if immunological reje ction could be prevented. Pig embryonic neural tissue has been grafted to p atients with Parkinson's disease, but no functional benefits have clinicall y been proven so far. The immune reactions to neural xenografts were incomp letely characterized at the time of these early clinical trials, and it is likely that the treatments used were insufficient and that the grafts were rejected. In this article we will review new experiments addressing the imm une responses against porcine neural tissue grafted to the adult brain, inc luding the role of antibodies, complement, natural killer (NK) cells, lymph ocytes, as well as the effects of immunosuppressive drugs and donor tissue modifications.