HNAantigen

HNAantigen refers to Human Neutrophil Antigens. These are polymorphic antigens found on the surface of neutrophils, which are a type of white blood cell. Polymorphism means that different individuals can have different versions of these antigens. HNA antigens are determined by genetic variations in specific genes, primarily located on chromosome 7.

The HNA system is important for several reasons. It plays a role in transfusion medicine, particularly in cases of transfusion reactions. If a patient receives a blood product containing neutrophils with HNA antigens that they do not possess, their immune system can produce antibodies against these foreign antigens. This can lead to alloimmunization, where the recipient develops antibodies against the HNA antigens of the donor. Subsequent transfusions can then result in adverse reactions, including febrile non-hemolytic transfusion reactions or, in more severe cases, transfusion-related acute lung injury (TRALI).

HNA antigens are also implicated in neonatal alloimmune neutropenia (NAIN). This occurs when a mother produces antibodies against her infant's neutrophil antigens, which are inherited from the father. These maternal antibodies can cross the placenta and destroy the infant's neutrophils, leading to a dangerously low neutrophil count, increasing the risk of infection.

The HNA system comprises several different antigen systems, with the most well-characterized including HNA-1, HNA-2, HNA-3, HNA-4, and HNA-5. Each system is defined by specific alleles and associated genes. For instance, HNA-1 is associated with the FCGR3B gene, while HNA-4 is associated with the ITGB2 gene. Understanding these antigens and their genetic basis is crucial for accurately diagnosing and managing HNA-related conditions.