Human Platelet Antigen (HPA)

Human Platelet Antigen (HPA) refers to specific markers found on the surface of platelets, which are blood cells responsible for clotting. These markers are inherited genetic variations that differ among individuals. HPAs are important because if a person’s immune system encounters incompatible HPAs—such as through transfusions or pregnancy—it can recognize these markers as foreign and produce antibodies against them. This immune response can lead to conditions like neonatal alloimmune thrombocytopenia or platelet transfusion refractoriness, affecting blood clotting and increasing bleeding risk. Understanding HPAs helps improve blood transfusion safety and manage certain immune-related platelet disorders.