HLA proteins and cytotoxic antibodies
You have a combination of A,B and DR HLA proteins inherited from your parents. When you are exposed to other HLA proteins your immune systems attacks them. Your body then develops antibodies against these HLA proteins. If you have already have antibodies against a donor cell HLA protein then your body may attack those donor cells and reject the donor kidney.
When you are tissue typed, a blood test is taken to determine your HLA proteins and cytotoxic antibodies. This is usually one of the first steps in your transplant work-up. Your HLA proteins and cytotoxic antibodies can also change overtime, so these test will be repeated every one to two months.
You will share some HLA proteins with other people and the more you share the more likely your body is to accept their kidney. How similar your tissue typing is with someone else’s refers your “HLA-match”. This is usually given as a number out of six as there were six groups of protein identified many years ago that were found to be important.
For many people, HLA-matching is less important than it was a few decades ago. This is because the anti-rejection medications have improved. We also understand more about tissue typing than we used to, and this has led to longer survival of transplanted kidney.