Tissue Type Test

Histocompatibility Testing, HLA (Human Leukocyte Antigen), Human Leukocyte Antigen (HLA)

Test Overview

A tissue type test is a blood test that measures substances called antigens 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 platelets). 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 autoimmune diseases.

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 multiple sclerosis or ankylosing spondylitis) 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 all of the body's 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.

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Author:	Jan Nissl, RN, BS Susan Van Houten, RN, BSN, MBA	Last Updated: December 4, 2006
Medical Review:	Patrice Burgess, MD - Family Medicine Andrew Swan, MD, CCFP, FCFP - Family Medicine Joseph O'Donnell, MD - Hematology/Oncology
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