HLA typing; Tissue typing
A histocompatibility antigen blood test looks at proteins called human leukocyte antigens (HLAs). These are found on the surface of almost all cells in the human body. HLAs are found in large amounts on the surface of white blood cells. They help the immune system tell the difference between body tissue and substances that are not from your own body.
Blood is drawn from a vein. You may feel slight pain or a sting when the needle is inserted. Afterward, there may be some throbbing.
How to Prepare for the Test
You do not need to prepare for this test.
Why the Test is Performed
The results from this test can be used to identify good matches for tissue grafts and organ transplants. These may include kidney transplant or bone marrow transplant.
It may also be used to:
- Diagnose certain autoimmune disorders
- Determine relationships between children and parents when such relationships are in question
- Monitor treatment with some medicines
You have a small set of HLAs that are passed down from your parents. Children, on average, will have half of their HLAs match half of their mother's and half of their HLAs match half of their father's.
It is unlikely that two unrelated people will have the same HLA makeup. However, identical twins may match each other.
Some HLA types are more common in certain autoimmune diseases. For example, HLA-B27 antigen is found in many people (but not all) with ankylosing spondylitis and Reiter syndrome.
Slight risks from having blood drawn may include:
- Excessive bleeding
- Fainting or feeling lightheaded
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
Fagoaga OR. Human leukocyte antigen: the major histocompatibility complex of man. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 23rd ed. St Louis, MO: Elsevier; 2017:chap 49.
Wang E, Adams S, Stroncek DF, Marincola FM. Human leukocyte antigen and human neutrophil antigen systems. In: Hoffman R, Benz EJ Jr, Silberstein LE, Heslop HE, Weitz JI, Anastasi J, eds. Hematology: Basic Principles and Practice. 6th ed. Philadelphia, PA: Elsevier Saunders; 2013:chap 114.