Antibodies to human neutrophil antigen HNA‐3b implicated in cases of neonatal alloimmune neutropenia

BACKGROUND:Neonatal alloimmune neutropenia results from maternal alloimmunization to human neutrophil antigens. The alloantibodies involved in neonatal alloimmune neutropenia are against human neutrophil antigens HNA-1a, HNA-1b, HNA-1c, HNA-1d, HNA-2, HNA-3a, HNA-4a, HNA-4b, and HNA-5a; however, to date, antibodies specific to HNA-3b have not been reported. STUDY DESIGN AND METHODS:Blood samples from 10,000 unselected neonates were analyzed, resulting in the selection of 88 neutropenic newborns (neutrophil count <1.5 × 109 /L) from 83 mothers (three pairs of twins and one triplet). HNA-3 genotyping was performed by polymerase chain reaction-restriction fragment length polymorphism to identify the cases of maternal-fetal HNA-3 incompatibility. Serologic studies for detecting maternal HNA-3 alloantibodies were performed with the granulocyte agglutination test, the white blood cell immunofluorescence test, and a LABScreen Multi-HNA Kit. RESULTS:Genotyping studies identified 13 of 88 (14.8%) instances of maternal-fetal HNA-3 incompatibility, with all mothers typed as HNA-3a/a and neonates typed as HNA-3a/b. Serologic studies revealed that five of 13 (38.5%) mothers carried anti-HNA-3b plus human leukocyte antigen antibodies and that three of 13 (23.1%) mothers had anti-HNA-3b without human leukocyte antigen antibodies. CONCLUSION:Here, we report the first three cases of neonatal alloimmune neutropenia associated with HNA-3b antibodies resulting in a neonatal alloimmune neutropenia incidence of one in 3333 live births.