Primary structure of human neutrophil antigens 1a and 1b

• Published in: Transfusion (Philadelphia, Pa.) Pa.), 2020-04, Vol.60 (4), p.815-821
• Main Authors: Sachs, Ulrich J., Radke, Clemens, Bein, Gregor, Grabowski, Claudia, Simtong, Piyapong, Bux, Jürgen, Bayat, Behnaz, Reil, Angelika
• Format: Article
• Language: English
• Subjects: Alloantibodies; Amino acid sequence; Amino acids; Antibodies; Antigens; Antisera; Asparagine; Epitopes; Genotypes; Immunization; Immunoglobulin G; Immunoglobulins; Neutrophils; Pattern analysis; Permutations; Phenotypes; Receptors; Serine
• ISSN: 0041-1132; 1537-2995
• DOI: 10.1111/trf.15707

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.