Hemostasis in Xenotransplantation

The recent revival of interest in xenotransplantation across discordant species focused initially on immunological aspects of hyperacute rejection. More latterly, research has explored the effects of antibody and complement binding to the endothelial cell. However the ultimate end-point of hyperacute rejection (the xenograft reaction) can be considered to be microvascular thrombosis. Thus hemostasis, the complex system which maintains the fluidity of blood within a vessel, but forms a clot once the vessel wall is breached, is an obligatory component of the xenograft reaction. This chapter will cover a basic understanding of hemostasis and then discuss the relative importance of hemostatic activation in the pig-to-human xenograft reaction.