Two cases of maternal alloimmunization against human neutrophil alloantigen‐4b, one causing severe alloimmune neonatal neutropenia

Human neutrophil antigen (HNA)-4a/4bw is encoded by 230G>A in ITGAM, which results in an Arg61His substitution of the αM chain (CD11b) of complement receptor 3 (CR3; CD11b/18 or Mac-1). HNA-4a antibodies have been detected in the sera of female blood donors and in maternal sera that caused alloimmune neonatal neutropenia (ANN), in which maternal immunoglobulin (Ig)G antibodies against a paternally inherited HNA cross the placenta and destroy...