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Human Leukocyte Antigens (HLA) explained

What is HLA?

HLA stands for Human Leukocyte Antigens. HLA are protein structures that are found on most of the cells in your body and their role is to help your immune system to identify foreign items. This is important for your body to stay healthy. Any proteins that are not recognized as belonging to your body are destroyed by the immune system. The immune system will destroy these foreign items and will make antibodies to them so they will recognize them in the future and target them for removal. These antibodies will often be present for the rest of your life to help keep your body protected.

HLA Typing

You inherit your HLA type from your parents. Half of it comes from your mother and the other half from your father. Since the HLA structures are found on almost all cells of the body, HLA typing is also known as “tissue typing.” HLA typing is primarily used to help match patients needing a bone marrow or organ transplant with a compatible donor.

Patients needing frequent platelet transfusions sometimes form antibodies and may then require HLA matched platelet donors. At Carter BloodCare, a selection of frequent platelet donors will have limited HLA typing performed so that compatible donors can be quickly found for these patients.

HLA and Blood Donation

If cells with a different HLA type enter your body, due to pregnancy, transfusion or transplantation, your immune system might see them as foreign and form antibodies against them.

These antibodies often appear in women after multiple pregnancies. During pregnancy, the placenta protects the fetus from being harmed by these antibodies, but the antibodies will be present in the mother for the rest of her life.

The antibodies are present in the plasma part of your blood and there is a small risk that a patient needing a transfusion will have a reaction to those antibodies. The reaction can lead to a serious lung injury in the patient.

Because of this risk, Carter BloodCare asks all blood donors about pregnancy history. If the donor has been pregnant, a test to look for HLA antibodies will be performed. If the test is positive for HLA antibodies, then the donor will not be able to donate plasma or platelets. However, this donor can still make a positive impact by donating whole blood or double red cells if they qualify.