What is tissue typing?

It really requires a highly tuned medical or scientific brain to understand tissue typing!

The first point to make is the easiest one to understand, and it is this:  Matching a potential bone marrow donor to a patient has nothing to do with blood type.  And that is an important point to understand.  Whereas there are several different "blood types" there are tens of thousands of different possible "tissue types".

Are you ready for it to get complicated?  If you are, then read on.  The difficulty in finding a suitable donor lies in the fact that the donor's and patient's "tissue type" must closely match in order for the transplant to be successful.  Genetic markers on the surface of white blood cells called HLA-antigens define a person's tissue type.  Since these genetic markers are inherited, siblings are much more likely to have similar HLA-antigens than unrelated persons. 

There's about a 30 percent chance that a patient's sibling will be a suitable donor. (i.e. a one-in-four chance of any one sibling being a match, with increased odds in larger families). If a donor must be located in the general population, the chances of finding a match range from one in 1,000 to one in several million, depending on the frequency of the patient's tissue type in the general population.

And that is about enough for me to take in.  How about you?  A key point is that it is an incredibly specialised as well as complex issue.  It involves white cells, chromosomes and DNA testing.

If you have an appetite for this sort of stuff the follow this link to delve deeper!