The immunogenicity of porcine tissue is a major obstacle to its use as donor material in xenotransplantation for neurodegenerative diseases. We are currently evaluating a novel strategy for reducing the immunogenicity, in which the alpha-galactosyl epitope (Galalpha1,3Galbeta1,4GlcNAc-R) is used as a target for antibody- and complement-mediated removal of microglia. In the present study, our aim was to determine whether a pretreatment with antibodies against the alpha-galactosyl epitope (anti-Gal) and complement would lyse or otherwise damage dopaminergic neurons in porcine embryonic ventral mesencephalon (VM), the donor tissue for treatment of Parkinson's disease by xenotransplantation. Cell suspensions prepared from VM tissue from 27-day-old pig embryos were incubated with anti-Gal, purified from normal human serum by affinity chromatography, or medium only (control), and subsequently with rabbit complement. After these pretreatments, the cell suspensions were transplanted into the right striatum of 14 adult rats (two groups of 7 animals). The animals were sacrificed 20 days after transplantation, the brains were processed for histology, and the sections were stained for Nissl substance, porcine neurofilament, tyrosine hydroxylase, and rat CD45 to determine graft volume, presence of porcine neurons, content of dopaminergic cells, and leukocyte infiltration, respectively. The VM tissue pretreated with anti-Gal and complement gave rise to dopaminergic grafts that were indistinguishable from those derived from VM tissue given the control pretreatment. In 5 of the 14 animals, the grafts were infiltrated by host leukocytes, but in two of these recipients, the infiltration was only minimal. We conclude that anti-Gal and complement can be applied to porcine embryonic VM tissue without damaging the dopaminergic neurons and their precursors.