Test Overview
A tissue type test is a blood test that measures
substances called
on the surface of body cells and tissues.
Checking the antigens can tell if donor tissue is safe (compatible) for
transplant to another person. This test may also be called HLA typing. Antigens
can tell the difference between normal body tissue or foreign tissue (for
example, tissue from another person's body). Tissue type helps find the best
match for tissues or blood cells (such as
). In some cases, a tissue type test may be
done to see whether a person has a chance for developing certain diseases that
cause the body to attack its own cells, such as
.
A special pattern of
antigens (called tissue type) is present on each person's cells and tissues.
Half of each person's antigens come from (inherited) the mother and half from
the father. Identical twins have the same pattern, but everyone else has his or
her own special pattern. Brothers and sisters have a 1-in-4 chance of having an
identical match. Each person's antigen pattern can be "fingerprinted" through a
tissue type test.
- The closer the match of antigens, the more
likely that transplanted tissues or organs will not be
rejected.
- The more similar the antigen patterns are from two
people, the more likely it is that they are related.
- Some diseases
(such as
or
) are more common in people who
have certain antigen patterns. The reason for this is unknown.
Two main antigen groups are used for a tissue type test.
Class I has three classes of antigens (HLA-A, HLA-B, HLA-C) that are found on
some kinds of blood cells. Class II has one class of antigens (HLA-D) that are
found only on certain cells in the body. There are many different types of
antigens in each category.