Antibodies to human neutrophil antigen HNA-4b implicated in a case of neonatal alloimmune neutropenia

BACKGROUND Maternal alloantibodies directed against human neutrophil antigens (HNAs) can cause moderate‐severe neutropenia in the newborn in a condition known as neonatal alloimmune neutropenia (NAIN). Neonates with NAIN can present with sepsis or be asymptomatic. NAIN has previously been reported as caused by antibodies against HNA‐1a, ‐1b, and ‐1c; CD16b, ‐2, ‐3a, ‐4a, and ‐5a; and HLA, but not by antibodies against HNA‐4b. We report a case of NAIN due to anti‐ HNA‐4b alloimmunization in a term neonate. CASE REPORT An infant with persistent and marked neutropenia was suspected of having neonatal alloimmune neutropenia. Blood samples from both parents were investigated for HNA and HLA incompatibilities by molecular typing techniques and the mother for the presence of HNA and HLA antibodies by serologic techniques. RESULTS Initial results indicated the presence of granulocyte antibodies in the maternal serum, the specificity of which were shown to be anti‐HNA‐4b. Subsequently, the mother was genotyped as HNA‐4b negative and the father as heterozygous HNA‐4ab. The child was shown to have inherited the incompatible HNA‐4b allele. CONCLUSION We have demonstrated the first case of NAIN due to maternal alloimmunization against HNA‐4b, pending ratification by the International Granulocyte Immunobiology Workshop.