And the host immune cells, for example, cytotoxic T cells will be able to distinguish this host cell from some type of foreign pathogen as a result of these self antigens present on the MHC protein. Now, if we basically transplant a graft, a tissue or an organ that contains cells with a different MHC protein, with a different major histocompatibility complex that contains a different cell antigen, then the host immune cell will label this cell as being pathogenic, as being foreign. And what will happen is this cell will destroy that graft cell along with that entire allograft. And what this cytotoxic T cell does specifically is it binds onto this complex and it initiates the release of powerful digestive proteins. And those proteins drill holes in the membrane of these grass cells and that ultimately lyses and destroys the cell. So this is the major problem that is involved with the transplantation and grafting process, the actual immune system of that host organism, host individual destroying that transplanted tissue or organ.