Transplant rejection

[Bert]

I've read somewhere that a person's body is constantly changing. Cells die and are replaced (except brain cells) . I think our skin is renewed every three weeks, for instance. Some body parts change on a much slower basis, but I believe that everything is changed aftere 7 years. I'm not sure if that includes teeth and bone, probably not, but at least all the soft tissues and organs. If this is true, why do transplant patients need to take anti-rejection drugs for the rest of their lives, since the cells that die in the transplanted organ must (I presume) be replaced by cells made by the recipients body?

[Hamish]

Great question, got me thinking. I'm no expert on this but... An organ that is transplanted is alive. The process of regeneration is by cell division, therefore the genetics of the transplated organ will remain the same and the tissue will express the same protine markers that identify it as a 'forigen body' therefore the body need to be fool into accepting the organ for the rest of the persons life. (is this clear?) hope that helps, but perhapse someone elese had a better explanation.

[andy hughes]

Hamish is quite right - the human body will natruallly reject any 'foreign' interloper - this even extends to a developing foetus - the symptoms of rejection are consolidated in morning sickness, although in the interest of procreation, the female body does adapt to the interloper and accepts and develops it. Organ transpants remain as 'invaders' for the duration, and the host body has to be prevented from serious rejection symptoms, which can be fatal.