An abstract recently published in Vox Sanguinis provides updates on the Polish Platelet Donor Registry, which is intended to improve the identification of matched platelets for fetal and neonatal alloimmune thrombocytopenia (FNAITFetal and neonatal alloimmune thrombocytopenia A rare condition in which a mother’s immune system attacks fetal platelets, leading to dangerously low platelet levels before and/or after birth.) and other conditions.
Most cases of FNAIT result from incompatibility between the human platelet antigenHuman platelet antigen Proteins found on the surface of platelets. Incompatibility between maternal and fetal human platelet antigens can trigger FNAIT. (HPAHuman platelet antigen Proteins found on the surface of platelets. Incompatibility between maternal and fetal human platelet antigens can trigger FNAIT.) of the mother and fetus, which results in the production of antibodies that attack fetal platelets. Human leukocyte antigen (HLA) can also contribute to FNAIT, either as a direct trigger or as a promotor of the immune response against HPA. Platelet matching means that the newborn receives a platelet transfusionPlatelet transfusion A treatment for newborns with very low platelet counts that ideally uses HPA-compatible or washed maternal platelets. from a donor whose platelets do not contain the antigens that the mother’s immune system is attacking.
Blood transfusion centers throughout Poland provided 3,110 blood samples to the registry between 2022 and 2025. Of these, the researchers tested 2,996 samples to determine their HPA and HLA status. Prior to this effort, only 17% had known HLA types, and 3.3% had known HPA-1a status.
Every person inherits two copies of the HLA-A gene and two copies of the HLA-B gene. In the registry, 15% of donors had identical copies of their HLA-A gene, 11% had identical copies of their HLA-B gene, and 2.1% had identical copies of both. Donors who inherit the same copy, known as homozygous, can sometimes be easier to match with recipients because they have simpler antigen profiles.
Read more about FNAIT causes and risk factors
The study also uncovered individuals who were homozygous for rare HPA variants, including HPA-1b (3%), HPA-2b (1%) and HPA-5b (1%). On the other hand, nearly half of donors were homozygous for HPA-1a, HPA-2a and HPA-5a.
Using the registry, 49 patients with alloimmunizationAlloimmunization The process by which the mother becomes sensitized to fetal platelet antigens and begins producing alloantibodies. This is what causes FNAIT. received matched platelet transfusions. Of these, 28 had only anti-HLA antibodies, 5 had only anti-HPA antibodies, and 16 had both anti-HLA and anti-HPA antibodies. Only 50% of recipients received fully matched HLA matched platelets, highlighting the need for continued growth of the registry to improve donor availability.
In developing this registry, the Polish Ministry of Health is moving closer to its goal of “ensuring the self-sufficiency of the Republic of Poland in blood and blood components for the years 2021-2026.”
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