Human neutrophil antigens (HNAs) are carried on five different glycoproteins on human neutrophils. The HNA nomenclature system follows a similar convention to that used for human platelet antigen nomenclature (1). Neutrophils do not express ABO or other red cell group antigens, but do express HLA Class 1 and 2 antigens upon activation.
Antibodies to HNA have been implicated in:
• Febrile non-haemolytic transfusion reactions (FNHTR)
• Transfusion-related acute lung injury (TRALI)
• Neonatal alloimmune neutropenia
• Autoimmune neutropenia
• Immune neutropenia after bone marrow transplant
Neonatal alloimmune neutropenia is caused when maternal antibodies attack the fetal neutrophils. HNA-1a, HNA-1b and HNA-2 antigens are implicated in this condition.
Autoimmune neutropenia in adults may be idiopathic or secondary due to rheumatoid arthritis, systemic lupus erythematous or bacterial infections. In infancy the autoantibody is directed against HNA-1a or -1b in about 30% of cases. The condition is usually self-limiting and relatively benign. Recovery takes between 7 – 24 months.
The detection of neutrophil antibodies requires specialist testing such as the granulocyte agglutination test (GAT) (3), granulocyte immunofluorescence test (GIFT) (3) and HNA typing.
1. Flesch BK. Human neutrophil antigens: a nomenclature update based on new alleles and new antigens. ISBT Science Series 2015;10:243-249.
2. AABB Technical Manual. 18th ed. USA, 2014.
3. Heinzl MW, Schonbacher M, Dauber EM, Panzer S, Mayr WR, Kormoczi GF. Detection of granulocyte-reactive antibodies: a comparison of different methods. Vox Sanguinis 2014;108:287-293.