HNAantigens

HNAantigens, also known as Human Neutrophil Antigens, are polymorphic antigens found on the surface of human neutrophils. These antigens are determined by variations in genes that encode for proteins on the neutrophil cell membrane. The most well-studied HNA systems are HNA-1, HNA-2, HNA-3, HNA-4, and HNA-5, each defined by specific genetic loci and associated molecular structures. For instance, HNA-1 antigens are associated with the FcγRIIIb receptor, HNA-2 with CD177, HNA-3 with a chemokine receptor (CXCR2), HNA-4 with integrin αM (CD11b), and HNA-5 with integrin αL (CD11a).

The presence or absence of specific HNAantigens can vary significantly among different ethnic populations. This genetic polymorphism is important in various clinical contexts. One of the primary clinical implications of HNAantigens is in transfusion medicine, particularly in cases of neonatal alloimmune neutropenia (NAIN) and transfusion-related acute lung injury (TRALI). NAIN occurs when maternal antibodies against fetal neutrophil antigens cross the placenta, leading to neutropenia in the newborn. TRALI can be triggered by the transfusion of plasma containing antibodies that react with the recipient's HNAantigens on neutrophils.

Understanding HNAantigen profiles is crucial for matching blood donors and recipients to prevent immune reactions. Genetic testing for HNA typing is employed to identify individuals with specific antigen profiles, aiding in the selection of compatible blood products for patients at risk of alloimmunization. Research continues to identify new HNA systems and to further elucidate their roles in immune responses and disease pathogenesis.