Now, another important complication is actually the opposite of this. So this is called graft versus host disease or gvhg. So let's suppose we're transplanting some type of tissue or organ from one individual to a different individual. And this particular organ contains a high concentration of T cells, of white blood cells. And one example of such an organ, such a tissue is bone marrow. So let's suppose we're transformed, we're transferring bone marrow from one individual to a different individual.