CD4+ cells play a major role in xenogeneic human anti-pig cytotoxicity through the fas/fas ligand lytic pathway

In this study, the role of cell-mediated cytotoxicity by human leukocytes against pig endothelial cells was examined in vitro. The aim was to determine which cell subsets were responsible for this phenomenon and which pathways were involved in cell lysis. Primed human peripheral blood mononuclear cells (PBMC) or purified CD4+ or CD8+ T cells were used in a cell-mediated cytotoxicity assay in which cytotoxicity of an SV40 transformed porcine endothelial cell (EC) line (SVAP) was determined by Annexin V binding. Human PBMC demonstrated specific lysis of porcine EC that was proportional to the effector: target ratio. CD4+ T cells accounted for >60% of this lysis, whereas CD8+ T cells accounted for