Good question, and here is some info from Alloderm:

"Donated human skin tissue supplied by US AATB-compliant tissue banks is aseptically processed using LifeCell's proprietary technique to remove the epidermis and cells that can lead to tissue rejection and graft failure. The result is an intact acellular matrix of natural biological components that promotes rapid revascularization, white cell migration and cell repopulation, as shown in animal studies."

My ENT needed to use Alloderm since he did not plan on a RND, I was supposed to just have a MRND, otherwise he would have done a flap. Luckly, the neck muscle was removed, since it contained cancer. The Alloderm had to be removed in a subsequest surgery, peeled off carotid artey, to do a pec flap for a different reason other than tissue failure, which was not enough protection on the carotid artery for additional radiation.