World human neutrophil antigens investigation survey.

BACKGROUND AND OBJECTIVES: Human neutrophil antigens (HNAs) are categorized into five systems: HNA-1 to HNA-5. Given the importance of neutrophils in immunity, we sought to create awareness of the role of HNA diagnostic services in managing immune neutropenia and transfusion-related acute lung injury. To provide health communities all around the world with access to these services, we conducted a survey to create a directory of these HNA diagnostic services. MATERIALS AND METHODS: An Excel table-based survey was created to capture information on the laboratory's location and was emailed to 55 individuals with known or possible HNA investigation activity. The collected data were then summarized and analysed. RESULTS: Of contacted laboratories, the surveys were returned from 23 (38.2%) laboratories; 17 have already established HNA diagnostic (of them 12 were regular participants of the International Granulocyte Immunobiology Workshop [ISBT-IGIW]), 4 laboratories were in the process of establishing their HNA investigation and the remaining 2 responder laboratories, did not conduct HNA investigations. In established laboratories, investigation for autoimmune neutropenia (infancies and adults) was the most frequently requested, and antibodies against HNA-1a and HNA-1b were the most commonly detected. CONCLUSION: The directory of survey respondents provides a resource for health professionals wanting to access HNA diagnostic services. The present study offers a comprehensive picture of HNA diagnostics (typing and serology), identifying weak points and areas for improvement for the first time. Identifying more laboratories involved in HNA diagnostics with limited access to international societies in the field will globally improve HNA diagnostics.

Anti-human neutrophil antigen-1d specificity is frequently observed in anti-human neutrophil antigen-1b alloantisera.

BACKGROUND: Four amino acids are involved in epitope formation of human neutrophil antigens (HNA)-1 alleles, located at positions 36, 65, 78, and 82. HNA-1a and HNA-1b alloantibody epitopes were recently characterized. The HNA-1b allele also carries the HNA-1d epitope p.78A&p.82N. The current study aimed to identify compound antibody specificities in HNA-1b alloantisera, especially the presence of anti-HNA-1d. STUDY DESIGN AND METHODS: For investigation of binding epitopes for HNA-1b alloantibodies, cells stably expressing different HNA-1 alleles were generated and tested against previously well-characterized HNA-1b antisera (n = 11) in an antigen capture assay. Sera with p.82N specificity or p.36S and p.82N specificity were additionally analyzed using adsorption and elution methods. RESULTS: Three amino acids, p.36S, p.78A, and p.82N, are involved in epitope formation of HNA-1b. The following specificities were identified in 11 HNA-1b alloantisera: p.36S (6/11), p.82N (9/11), and p.78A&p.82N (8/11), of which p.36S was identified as a sole entity in 2/11, whereas 9/11 antisera contained a polyspecific mixture of anti-p.36S, p.82N (1/11), and anti-p.78A&p.82N in combination with anti p.82N (5/11) or compound specificities of anti-p.36S, p.82N, and p.78A&p82N (3/11). In seven of eight antisera with p.82N specificity, anti-p.78A&p.82N was detected. DISCUSSION: Analysis of HNA-1b antisera indicates compound specificities for HNA-1b alloantibodies with a high variation between HNA-1b immunized individuals. Amino acids p.36S, p.82N, and p.78A&p.82N are necessary for HNA-1b epitope formation. The HNA-1d epitope is recognized by 73% (8/11) of HNA-1b immunized individuals.

Primary structure of human neutrophil antigens 1a and 1b.

BACKGROUND: Neutrophil specific Fcγ receptor IIIb (CD16b) is a low-affinity IgG receptor. Its polymorphic variants are associated with human neutrophil antigens (HNA). HNA-1a and HNA-1b differ in four amino acids. Immunization can lead to the production of alloantibodies. The exact contribution of four amino acid exchanges for the formation of HNA-1a, -1b epitopes is currently unknown. STUDY DESIGN AND METHODS: Permutation of each polymorphic amino acid from wild-type CD16b cDNA constructs was performed and expressed on HEK293 cells. All 16 receptor variants were produced and tested against 19 well-characterized HNA antisera in an antigen capture assay. RESULTS: Analyzing the reaction pattern revealed that anti-HNA-1a antibodies can bind whenever asparagine (N) is present in position 65, regardless of the three other positions (CD16b *N**). Anti-HNA-1b antibodies can bind when serine (S) is present in position 36 (CD16b S***), when N is present in position 82 (CD16b **N*), or both (CD16b S*N*). CD16b variants with N65 and S36 and/or N82 (such as CD16b SNN*) bind both, anti-HNA-1a and anti-HNA-1b alloantibodies. If these specific amino acids are missing (as in CD16b RSD*), no antibodies will bind. CONCLUSION: Whereas the primary structure of HNA-1a and HNA-1b usually differs in four amino acids, epitope composition is not "antithetical". N65 alone determines the presence of HNA-1a, and S36 and/or N82 determine the presence of HNA-1b. Amino acid 106 does not participate in epitope formation. Our findings are of specific relevance when a HNA-1 phenotype is predicted from a genotype.