Immunoprotection of therapeutic cell transplants by encapsulation

The inflammatory response to an allogeneic or xenogeneic tissue transplant by the recipient is complex and includes both the specific immune response, and the non-specific response resulting from damage during implantation, ischaemic reperfusion injury and partial necrosis of the transplanted tissue. Transplantation of allogeneic or xenogeneic tissue within a biomembrane requires that the biomembrane be biologically inert, and that the mean pore size is adequate to allow the passage of oxygen and nutrition of the enclosed tissues, egress of the desired hormone or growth factor, while protecting the enclosed tissue from both the specific and non-specific responses of the host.