Human leukocyte antigen class 1 (HLA-1) alloimmunization during platelet transfusions can be influenced by a variety of factors, and doctors should aim to limit these complications, especially among vulnerable patients, according to a study recently published in Current Opinion in Immunology.
Platelet transfusions are often used to treat fetal and neonatal alloimmune thrombocytopenia (FNAIT).
In simple terms, alloimmunization is a process in which the immune system is abnormally directed against antigens from individuals that belong to the same species. Typically, the immune system is activated when confronting foreign, possibly dangerous substances, also called antigens.
Platelets are a group of red blood cells that are known to significantly express HLA-1. The density of HLA-1 differs between individuals and is a factor that doctors may take into consideration when choosing blood products for patients. Scientists think that the ability of platelet concentrates to trigger an immune response can at least be partly attributed to the type and quantity of HLA molecules expressed on the surface of platelets.
The anti-HLA immune response seen in some recipients of platelet transfusions is not fully understood. While some patients become alloimmunized after a single HLA-mismatched platelet transfusion, others only experience alloimmunization after repeated exposure. Scientists have various theories regarding why this is the case, but pinpointing an exact cause is challenging because of the multifactorial nature of these responses.
Read more about FNAIT testing and diagnosis
Generally, these responses can be broadly categorized as being influenced by one of three factors: the donor, the blood product itself or the blood product recipient. When anti-HLA-1 alloantibodies develop in the patient from platelet transfusions, doctors have a limited number of strategies to remedy the situation.
“By exploring new cellular components of the alloimmune response and refining the manipulation of platelet products, future studies should make it possible to significantly limit the production of anti-HLA-I antibodies,” the authors of the study wrote. “The ulterior goal is to establish a blood product stewardship for patients at risk of severe complications due to HLA alloimmunity.”
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