Porcine endothelium supports transendothelial migration of human leukocyte subpopulations: anti-porcine vascular cell adhesion molecule antibodies as species-specific blockers of transendothelial monocyte and natural killer cell migration.

Abstract

In cases where hyperacute rejection has been prevented, pig to primate organ transplantation results in a delayed rejection mediated by graft-infiltrating leukocytes. The migration of human leukocytes across porcine endothelium is poorly characterized, but may offer targets for species-specific antirejection therapy. Transwell tissue culture inserts with endothelial cells growing on polycarbonate filters were used to characterize the migration of peripheral blood monocuclear cells and purified leukocyte subpopulations across pig and human endothelial cells and cell lines. Endothelial cell morphology was evaluated by scanning and transmission electron microscopy, and the contribution of different adhesion receptor pairs to transendothelial migration was evaluated by antibody blocking experiments. There were no evident quantitative or qualitative differences in the capacity of human and porcine endothelium to support transendothelial migration of human leukocytes [T, B, and natural killer (NK) cells, monocytes, and neutrophils]. Monocytes and large granular CD3+ lymphocytes migrated most efficiently across the endothelium. Antiporcine vascular cell adhesion molecule-1 antibodies blocked transendothelial migration of human monocytes and NK cells across tumor necrosis factor-alpha stimulated pig endothelium by at least 60%. Anti-CD18 antibodies had no effect on the migration of human NK cells across pig endothelium, whereas they partly blocked migration of NK cells across human endothelium and migration of monocytes across porcine endothelium. Interleukin-2 stimulated, but not unstimulated, T and NK cells were cytotoxic to porcine endothelium. Porcine endothelium supports transendothelial migration of human leukocyte subpopulations as efficiently as human endothelium. Incompatibilities in some adhesion receptor pairs may be compensated for by other adhesion receptor pairs, as exemplified by human NK cells whose migration across human, but not pig, endothelium was blocked by anti-CD18 antibodies. Antiporcine vascular cell adhesion molecule-1 antibodies may be used as species-specific blockers of transendothelial NK cell and monocyte migration, and as such may prove to be useful inhibitors of cellular organ xenograft rejection.