Foetal cells, in the early weeks after conception, are not fully differentiated, grow fast and adapt easily to messages from surrounding tissue in a host. They grow, differentiate and integrate to form a part of the host organ. Foetal tissues are therefore sought for transplantation. A whole range of ethical issues arise which need to be addressed rationally and objectively. Pigs are currently the animals of choice as the size of their organs and the anatomical and physiological loads they must carry are similar to those in man.
Attempts are on to engineer pigs which possess genetic material similar to that in man.
It is hoped that tissues and organs from such transgenic pigs when transplanted into patients will not be rejected. Problems would still remain in using pig tissue or organs in human transplantation. Of great concern is the possibility of transferring germs and viruses peculiar to pigs into man through transplanted tissues. The existence of species-specific infective diseases that limit themselves to that species is well known. The apprehension that tissues or organs transplanted from animal to man may convey infection or unwanted genetic abnormalities has prompted most countires, to ban all research on transplanting animal organs to human beings till this issue has been satisfactorily addressed.