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HLA-B27 Antigen
Alternate Names : Human Leukocyte Antigen B27
Definition
This is a blood test to detect the presence of HLA-B27 on lymphocytes (white blood cells). See also Histocompatibility antigens test.
In the past, this test was performed using serum that specifically reacts with HLA-B27 on the cells (known as serologic tissue typing). Newer methods are now available that use genetic testing to identify the type of HLA-B27 in a particular individual. The HLA-B27 gene is designated as HLA-B*2701, HLA-B*2702, etc.
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Why is the Test Performed?
The human leukocyte antigens (HLAs) are proteins present on the surface of all body cells that contain a nucleus, and are in especially high concentrations in white blood cells (leukocytes).
HLA antigens are the major histocompatibility antigens for tissue recognition. They are especially important in considering any type of tissue transplant, for example, kidney transplant or bone marrow transplant.
Many HLA antigens exist, but some are of special interest since they are more common in certain autoimmune diseases. For example, HLA-B27 is found in 80-90% of people with ankylosing spondylitis and Reiter's syndrome. However, HLA-B27 is also present in 5-7% of Caucasian people without autoimmune disease.
Using the new genetic testing methods, not all HLA-B27 genes are associated with an increased risk of developing ankylosing spondylitis (for example, HLA-B*2706 has not been shown to have an association). It is important to note that this test does not predict the development of autoimmune disease, and should not be used for this purpose.