Mother of three and Armed Services Blood Bank Center-Pacific Northwest staff member, Air Force Tech. Sgt. Caitlin Alexander, has always wanted to donate plasma. However, Alexander, like any other woman who had one or more pregnancies, was deferred from donating because of the possibility that she had developed an antibody to the human leukocyte antigen.

At the time, HLA testing was not available for blood donors.

“Being that I (have an) AB blood type, I know how important plasma is,” Alexander said. “But after my son was born I was told I could not donate plasma.”  She could not donate plasma until a HLA test was devised. Thanks to a recent regulation change, she might finally get her chance.

On May 1, the American Association of Blood Banks changed regulations to allow testing for the HLA, giving women who had been pregnant a chance to donate plasma products. The new regulation, however, will allow women who test negative to donate plasma or platelets. Women who test positive will be deferred from donating plasma products, but still allowed to donate whole blood.

HLAs are protein complexes found on the surface of most cells in the human body. They represent the primary immune-recognition factor for self vs. non-self responses. Each person has a set of HLA antigens that are inherited in genetic blocks from our parents – one block from each parent combines to create the whole antigen.

The body’s immune system produces HLA antibodies against HLA antigens that are different from its own, therefore, the immune system can be exposed to these foreign antigens through pregnancy, blood transfusions and tissue transplants.

Antibodies are important because they protect a person’s health by sticking to pathogenic substances, helping fight off infections and clear unwanted substances. However, in rare cases, HLA antibodies in donated blood may be harmful to some transfusion recipients.

Transfusion-Related Acute Lung Injury, or TRALI, is the most harmful condition associated with HLA antibodies. TRALI is a syndrome characterized by acute respiratory distress caused by white blood cell sequestration in lung tissue following transfusion from a blood product that has an HLA or other associated antibodies.   

Normally, HLA antibodies are not harmful to the person who made them, but HLA antibodies can interfere with platelet transfusions by killing the donated platelets before they have a chance to work. For this reason, patients receiving platelet transfusions are tested for HLA antibodies.

Some people do not develop HLA antibodies at all, despite exposure, while others develop the antibodies after minimal exposure. It is not clearly understood why this is so, but people are most likely to develop HLA antibodies from pregnancies, prior blood or platelet transfusions or organ transplants.

To determine if the potentially harmful antibody is in someone’s system a plasma sample – the liquid part of the blood ­– is mixed with different HLA antigens. If there are HLA antibodies in the plasma, it will react with the sample and give a positive result, typically through destroying HLA specific cells or causing a color-change reaction.

While there is still a chance that women who have been pregnant will be deferred from donating, the new HLA test opens the door for women to consider donating platelets and plasma for the first time in many years. 

For women like Alexander, that is a welcome and exhilarating idea.

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