Human neutrophil antigen 2 sequence‐based typing: Joining the hunt for the CD177 answer

Abstract

Background and Objectives: Isoantibodies to human neutrophil antigen 2 (CD177) have been associated with several clinical conditions but to date the molecular basis for altered or non-expression has not been determined. Reliance on phenotyping and crossmatch to investigate these neutropenic clinical cases are inconvenient for the patients and demanding of resources within the laboratory. Therefore, a molecular approach has been introduced to address both issues. Materials and Methods:A DNA panel of 100 randomly selected blood donors were collected and supplemented with 18 DNA samples from blood donors previously shown to be CD177 null. All DNA samples were sequence-based typed for all exons and observed polymorphisms recorded. The DNA from two families previously investigated for neonatal alloimmune neutropenia due to CD177 isoantibodies were also analysed. Results:The incidence of CD177 null could be associated with a known exon 7 single-nucleotide polymorphism in 16/21 known CD177 null samples, which is consistent with previously published findings. Two additional mutations that may lead to null expression were also identified, of which one may be novel. In both family investigations, this same mutation could also be observed in the maternal DNA sample. Conclusion:Based on these observations, introduction of CD177 genotyping into routine use would identify null expression in over 75% (16/21) of associated cases.In turn, this could significantly reduce the need for supplementary testing and associated inconvenience to patients while permitting increased efficiency of laboratory testing. An added benefit would potentially elucidate other clinically relevant mutations and associated antigenic targets.

An accurate genetic assay to identify human neutrophil antigen 2 deficiency

“…The SNP c.787A > T is a nonsense SNP that terminates the protein translation and causes the HNA‐2 expression defect. Our previous study revealed that c.787T homozygosity is the primary genetic determinant for HNA‐2 deficiency, 16 which was confirmed by independent studies from other groups 17,18,23,24 …”

“…Our newly developed genetic assays will enable the reliable prediction of risks for HNA‐2‐related diseases in humans and will facilitate the diagnosis and prognosis of HNA‐2‐associated human disorders. Most importantly, our assays will significantly reduce the requirement for labour‐intensive laboratory tests and the associated inconvenience of patients 18 …”

“…Most importantly, our assays will significantly reduce the requirement for labour-intensive laboratory tests and the associated inconvenience of patients. 18…”

“…CD177 gene located at chromosome 19q13.31 region contains nine exons (Figure 1). Recently, we and others unravelled the primary genetic mechanism of HNA‐2 deficiency and expression variations, which is caused by a nonsense single nucleotide polymorphism (SNP c.787A > T) within the CD177 coding region 16–18 . The HNA‐2 null allele (STP allele) with the nonsense c.787T substitution likely originated from ectopic allelic conversion of the CD177 pseudogene 17 .…”

“…Recently, we and others unravelled the primary genetic mechanism of HNA-2 deficiency and expression variations, which is caused by a nonsense single nucleotide polymorphism (SNP c.787A > T) within the CD177 coding region. [16][17][18] The HNA-2 null allele (STP allele) with the nonsense c.787T substitution likely originated from ectopic allelic conversion of the CD177 pseudogene. 17 CD177 pseudogene is highly homologous to CD177 and hinders the genetic analysis of CD177.…”