A lot of the supposedly 'medical' reasons for disqualifying people from being kidney donors are purely arbitrary, and derive more from transplant team members wanting to play God with other people's lives than from any real problems. I also question the general assumption made by the medical profession that they should bend over backward to screen people out of being donors, rather than to be aggressive in recruiting people to be donors. If the government can seize healthy people bodily by the military draft to make them fight some useless war which will risk their health and even their life, why shouldn't dialysis teams try to minimize the criteria for excluding someone from being a kidney donor to save the lives of people who have no kidneys? It would create a more equal, and thus a more fair, distribution of misfortune in society if kidney donors were allowed to bear a little risk of ill health by donating a kidney to someone who would suffer an enormous degree of illness from not having any kidney at all.
When i had my transplant in 92 my brother gave on of his to me. He was a "perfect" match. We were so close they said it was only found in twins. Perhaps due to the insurance problems that kidney lasted for a little over ten years. At the time i was offered two more kidneys from friends. I am glad i took my brothers. The other were a four match. Now i am on the list again and was told they can now transplant a three match cause they over load you with anti rejection meds. I wonder how bad that can be.
For both cadaver and living-donor kidneys, the more antigens that match the better, especially the antigen at the DR site, which seems to have a lot to do with eliciting the immune response. However, with living donors, even a 0-antigen match is acceptable provided the Landsteiner blood type (A,B,O), the Rhesus factor (positive or negative), and the antigen cross-matching results are acceptable.