So these are the two major problems, two major complications that accompany grafting an organ transplant. Now, another complication that is really no longer a complication because we have ways of dealing with it is infections. But this was the problem when organ transplant and grafting was at its beginning. So the donated tissue or organ may contain dangerous pathogens such as HIV, hepatitis B or hepatitis C, rabies, syphilis and many other different types of diseases and pathogens. So basically, if we're transplanting an organ that contains HIV into an individual that does not contain HIV that individual will obtain that HIV and will then be HIV positive. Now, this was a problem in the beginning but nowadays we have different types of ways of testing for these different types of viruses and pathogenic agents.