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Naturally occurring point mutation Cys460Trp located in the I‐EGF1 domain of integrin β3 alters the binding of some anti‐HPA ‐ 1a antibodies
Author(s) -
Holzwarth Sarah Theresa,
Bayat Behnaz,
Zhu Jieqing,
Phuangtham Roongaroon,
Fischer Lars,
Boeckelmann Doris,
Röder Lida,
Berghöfer Heike,
Schmidt Silke,
Bein Gregor,
Santoso Sentot
Publication year - 2020
Publication title -
transfusion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.045
H-Index - 132
eISSN - 1537-2995
pISSN - 0041-1132
DOI - 10.1111/trf.15960
Subject(s) - neonatal alloimmune thrombocytopenia , epitope , microbiology and biotechnology , hek 293 cells , antibody , antigen , wild type , semaphorin , flow cytometry , mutant , platelet , mutation , chemistry , biology , fetus , cell culture , immunology , receptor , biochemistry , genetics , pregnancy , gene
Background Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is caused by the destruction of platelets in the fetus or newborn by maternal platelet alloantibodies, mostly against human platelet antigen (HPA)‐1a. Recent studies indicate that two anti‐HPA subtypes exist: Type I reacts with epitopes residing on the plexin‐semaphorin‐integrin (PSI) and type II with plexin‐semaphorin‐integrin/integrin epidermal growth factor 1 (I‐EGF1) domains of the β3 integrin. Here, we evaluated whether a Cys460Trp mutation in the I‐EGF1 domain found in a patient with Glanzmann thrombasthenia can alter the binding of anti‐HPA‐1a. Methods Stable HEK293 cell lines expressing wild‐type and mutant αIIbβ3 and αvβ3 were generated to prove the reactivity of different antibodies against HPA‐1a. Results Flow cytometry analysis of wild‐type (Cys460) and mutant (Trp460) expressed on HEK293 cells showed equal surface expression of αIIbβ3 and αvβ3. When tested with mutant αIIbβ3 cells, reduced binding was observed in Type II but not in Type I anti‐HPA‐1a. These results could be confirmed with platelets carrying Cys460Trp mutation. Interestingly, reduced binding of Type I antibodies was detected with mutant αvβ3 cells. Both antibody types were found in maternal sera from FNAIT cases by an antigen‐capture assay with use of HEK293 transfected cells. Conclusions These observations confirm the existence of Type I and Type II anti‐HPA‐1a. Furthermore, this study underlines different immunogenicity of HPA‐1a antigen(s) residing on either αIIbβ3 or αvβ3. Further analysis of FNAIT cases from mothers having a fetus with and without intracranial bleedings with use of such an approach may highlight the functional relevance of different anti‐HPA‐1a subtypes.