Histocompatibility antigens

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Blood test

Histocompatibility antigens

Definition:

Histocompatibility antigens is a blood test that determines a person's major histocompatibility antigens.

Alternative Names:
HLA typing; Tissue typing
How the test is performed:

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic. An elastic band is placed around the upper arm to apply pressure and cause the vein to swell with blood.

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A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children:

The area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. A bandage may be applied to the puncture site if there is any bleeding.

How to prepare for the test:

No preparation is necessary.

For infants and children:

The preparation you can provide for this test depends on your child's age and previous experiences. For specific information regarding how you can prepare your child, see the following topics:

Infant test or procedure preparation (birth to 1 year)
Toddler test or procedure preparation (1 to 3 years)
Preschooler test or procedure preparation (3 to 6 years)
Schoolage test or procedure preparation (6 to 12 years)
Adolescent test or procedure preparation (12 to 18 years)

How the test will feel:

When the needle is inserted to draw blood, you may feel moderate pain, or only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the test is performed:

HLA (human leukocyte antigens) are proteins found in the membranes (outer coating) of nearly every cell in the body (all cells that have a nucleus). These antigens are in especially high concentrations on the surface of white blood cells (leukocytes).

HLA antigens are the major determinants used by the body's immune system for recognition and differentiation of self from non-self (foreign substances). There are many different major histocompatibility (HLA) proteins, and each person possesses only a small, relatively unique set that is inherited from their parents. It is unlikely that 2 unrelated people will have the same HLA make-up.