Reference no: EM132338590

Question

Dr. Triplett did a transplatnation experiment: He removed the pituitary (hypophysectomy) from developing tadpoles. He "parked" these pituitaries in other frogs while the hypophysectomized tadpoles developed into adults. Finally, he tranplanted the parked pituitaries back into the original (now adult) frog. The success of this graft was easily measured: Because the pituitary makes melanocyte stimulating hormone (MSH), hypophosectomized frogs are white. Thus, if the pituitary graft succeeded, the frog turned brown again and stayed that way. Indeed, all the frogs turned brown a day after their graft. However, within two weeks, all the frogs turned white again, indicating complete rejection. [Assume that the "parking" step did not change the pituitary in any way - Dr. Triplett controlled for this possibility in other experiments not described here].

 

• In as much as these grafts were the frogs' own pituitaries, does this break the "isografts succeed, allografts fail" rule?
• What does this experiment tell you about the underlying mechanism of the last property of the immune system - non responsiveness to "self?"

 

relevant notes:

non-responsiveness to self - implying that structures which are a normal part of the host organism are not attacked and destroyed by its own immune system, even though they could be attacked by the immune system of an individual in which they were not "self".

"isographs succeed, allographs fail": experiments showed that grafts between genetically identical individuals succeeded, whereas grafts between genetically different individuals failed.