The frequencies of HNA-3 genotypes in Brazilian blood donors is similar to that described in Caucasians; however, all Amerindians were HNA-3a/a, African Brazilians showed a lower frequency of HNA-3b/b, and Japanese had a higher prevalence of HNA-3b/b, suggesting that they may be at risk for developing anti-HNA-3a alloantibodies.

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.

Our data showed that the microbead-flow detected more HLA antibodies than ELISA, but the clinical significance of these antibodies is currently unknown. Detecting anti-HLA is useful for donor management and could contribute to the decision to definitively defer blood donors involved in TRALI incidents. However, further studies are necessary to better determinate the relative risk of TRALI induced by anti-HLA detected only by techniques with higher sensitivity rate.

Decreased CD11b expression can result in susceptibility to infectious diseases, impairment of phagocytic capacity. Decreased of CD40 expression can result in the decline in B lymphocyte activation. The other molecules studied presented alterations not significant, but compatible with the immunological changes in aging.

Summary Neonatal alloimmune neutropenia (NAIN) is caused by maternal alloimmunisation to fetal human neutrophil antigens (HNAs). This study investigated maternal HNA/HLA alloantibodies involved with NAIN and identified the frequency of NAIN in Brazilian neonates. Neonatal neutropenia (neutrophil count < 1.5 × 109/L) was investigated in samples from 10,000 unselected neonates, resulting in 88 neutropenic newborns (NBs) and their 83 mothers. Genotyping was performed by PCR‐SSP (HNA‐1/‐4) and PCR‐RFLP (HNA‐3/‐5). Serologic studies were performed by GAT (granulocyte agglutination test), Flow‐WIFT (white blood cells immunofluorescence test) and LABScreen‐Multi‐HNA‐Kit (OneLambda®) (LSM). Neonatal neutropenia was identified in 88/10,000 (0·9%) NBs. Genotyping revealed 60·2% maternal‐fetal HNA incompatibilities (31·8% for HNA‐1; 14·8% for HNA‐3; 15·9% for HNA‐4; 21·6% for HNA‐5). Serologic studies revealed 37·3% of mothers with positive results with at least one technique. The detected anti‐HNA specificities were confirmed in eight positive cases related to HNA‐1/‐3 systems. In cases with maternal‐fetal HNA‐4/‐5 incompatibility, no specific neutrophil alloantibodies were found but anti‐HLA I/II were present. Anti‐HNA‐2 was not identified. This is a large Brazilian study which involved the investigation of antibodies against all five HNA systems in neutropenia cases and showed a frequency of NAIN in 8/10,000 neonates. Among the HNA antibodies identified, we highlight the anti‐HNA‐1d and anti‐HNA‐3b, antibodies unusual in alloimmunised women, and rarely related to NAIN cases.