Serologic and molecular studies to identify neonatal alloimmune neutropenia in a cohort of 10,000 neonates
Samira Ali Abbas, Larissa Barbosa Lopes, Elyse Moritz, Juliana Oliveira Martins, Akemi Kuroda Chiba, Alessandra Midori Kunioshi, Elisama S. Barbosa, Dante Mário Langhi, Amélia Miyashiro Nunes dos Santos, Cárlei Heckert Godinho, José Orlando Bordin
Abstract
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 × 10 9 /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.