I recently saw a video about axolotls, and in the video they say that a limb from axolotl can be placed on another axolotl and it would attach itself. could we genetically engineer limbs like that to be attached onto a person.
Some thing like it:
It may be possible, given an advanced understanding of immunology, to grow human tissue with as few antigens on it as can be designed. Those that can't be eliminated can be matched to the most common antigen types, so a person in a hospital would be simply matched with a near-antigen match. One QZ-74-At-116-L model please! But this would be an approximation with genetically engineered tissues, and there would still be the risk of rejection.
Actually, the most likely scenario (this article is similar but not the same one, sorry) is that we will be able to simply make a person a new limb to match the existing one. You would isolate and replicate their stem cells, print a 3D matrix of bone and collagen with appropriate differentiation markers on them, then flood the structure with the stem cells which follow the developmental signals on the limb to become all the kinds of tissues you need for a new limb. The tissues will the extracellular matrix, shielding it from much of the immune system (properly designed, it won't be that immunogenic anyway) and the tissue will BE the person's tissue, so immunology won't be an issue.
While we can't yet print the 3D matrix, we have managed to dissolve off all of the tissue from mouse organs (a heart, in the case I saw) and then flood them with stem cells that repopulated the heart. So a heart from one mouse was denuded of cells, and the signals on the extracellular matrix left over were able to successfully colonize the heart framework and create a working heart that was then implanted in the new mouse without rejection.
So this may mean that in the near future, an organ donor won't need to be a match to the recipient, but that instead the organ will be stripped of tissue and repopulated with native cells. Once we work out the developmental signals for the organs, we should be able to print the structures to our desires. That means that if someone wanted to be taller, they could print longer legs and replace their short ones. Congenital heart defect? Print one without the flaw and grow a functional one instead. Heart wearing out? Grow a fresh one with native cells. Possibly grow and replace organ after organ, approaching the limits of what you can do to extend life. Only the brain would be a problem, since information would be difficult to transfer. But give it time...