Adhesion of subsets of human blood mononuclear cells to porcine endothelial cells

Cellular immune response is a major barrier to xenotransplantation, and cel l adhesion is the first step in intercellular recognition. Flow-cytometric adhesion assay has been used to investigate the differential adhesions of m onocyte (Mo), natural killer cell (NK) and T lymphocyte (T) present within human peripheral blood mononuclear cells (PBMC) to porcine aortic endotheli al cells (PAEC), and to demonstrate the effect of human interferon-gamma (h IFN- gamma) or/and tumor necrosis factor-alpha (hTNF-alpha) pretreatment of PAEC on their adhesiveness for different PBMC subsets. The preferential se quence for PBMC subset binding to resting PAEC is No, NK and T cells, among which T cells show the slightest adherence; hTNF-alpha can act across the species, and augment Mo, NK and T cell adhesion ratios by 40%, 110% and 3 t imes, respectively. These results confirm at the cell level that host Mo an d NK cells are major participants in the cellular xenagraft rejection, ther eby, providing a prerequisite for further studying the human Mo/NK-PAEC- in teractive mechanisms.