Human natural antibodies cytotoxic to pig embryonic brain cells recognize novel non-GaI alpha 1,3Gal-based xenoantigens

Transplantation of porcine embryonic brain cells, including dopaminergic ne urons, from ventral mesencephalon (VM) is considered a potential treatment for patients with Parkinson's disease. In the present study, we characteriz ed the distribution among VM cells of the major porcine endothelial xenoant igen, the Gal alpha 1,3Gal epitope, and evaluated the cytotoxic effect of a nti-Gal alpha 1,3Gal antibody-depleted and nondepleted human AB serum on VM cells. Overall levels of Gal alpha 1,3Gal-epitope expression was very low on the VM cell population using Bandeiraea simplicifolia IB4 lectin stainin g of resuspended VM cells in how cytometric analyses or staining of SDS-PAG E-separated, solubilized VM cell membrane proteins in Western blot analyses . Lectin-histochemical staining of sections of pig embryonal VM regions wit h BSA IB4 lectin showed staining restricted to endothelial cells and microg lia. In the presence of complement, both nondepleted and anti-Gal alpha 1,3 Gal antibody-depleted AB sera were shown to be cytotoxic to VM cells as ass essed in microcytotoxicity- and how cytometry-based cytotoxicity assays. Pu rified IgM and IgG were both cytotoxic in the presence of complement. Three major VM cell membrane antigens of approximately 210, 105, and 50 kDa were reactive with natural IgM antibodies present in pooled human AB sera. Thus , antibody-dependent cytotoxicity may contribute to pig to human brain cell xenorejection, necessitating donor tissue modifications prior to a more wi despread utilization of neural tissue xenografting. (C) 1999 Academic Press .