Alpha-gal-independent dual recognition and activation of xenogeneic endothelial cells and human naive natural killer cells

Background Interaction between vascularized xenograft and host immune syste m is thought to occur via Galactose alpha (1,3) Galactose (Gal alpha 1,3 ga l) structures decorating the xenograft. Methods. We raised anti-Gal alpha 1,3 gal-BSA polyclonal antibodies in babo ons and investigated effect(s) of these antibodies as well as soluble Gala 1,3 gal-BSA on human naive natural killer (Mi) cell interactions with porci ne aortic endothelial cells. Results, We demonstrate that human najive (unstimulated) Mt cells recognize xenogeneic endothelial cells under conditions where binding to the Gal alp ha 1,3 gal structures is minimized by the presence of blocking anti-Gal alp ha 1,3 gal IgG: or soluble Gal alpha 1-3 gal and in the absence of xenoreac tive natural antibodies and complement. After xenogeneic encounter both end othelial cells and human NH cells are activated. Endothelial cell activatio n is rapid and is manifested initially by an intraendothelial calcium trans ient and subsequently by expression of P-selectin and vascular endothelial cell adhesion molecule-1 on the xenoendothelium surface, NK cell activation is manifested by increased expression of perforin and increased cytotoxici ty towards the xenoendothelium, Neither recognition nor activation of the x enoendothelium was affected by the introduction of either anti-Gal alpha 1, 3 gal IgG or soluble Gal alpha 1-3 gal. Conclusion. Our data provide evidence that innate immune cells, such as NK cells, recognize and activate xenoendothelial cells independently of Gal al pha 1-3 gal structures and raise the possibility of novel interactive sites on both human naive NK cells and discordant xenogeneic endothelium.