Floch Aline, Lomas-Francis Christine, Vege Sunitha, Brennan Steven, Shakarian Gayane, de Brevern Alexandre G, Westhoff Connie M
Univ Paris Est Creteil, INSERM U955 Equipe Transfusion et maladies du globule rouge, IMRB, Creteil, France.
Laboratoire de Biologie Médicale de Référence en Immuno-hématologie moléculaire, Etablissement francais du sang Ile-de-France, Creteil, France.
Transfusion. 2023 Apr;63(4):798-807. doi: 10.1111/trf.17262. Epub 2023 Feb 4.
The basal cell adhesion molecule (BCAM) carries the antigens of the Lutheran (LU, ISBT005) system. We report a novel Lutheran antigen and propose an updated, full-length 3D model of BCAM.
Red blood cell testing, antibody identification, and BCAM genomic DNA sequencing were done by standard methods. Multi-template homology modeling of BCAM used structural templates selected for coverage, highest sequence identity, and protein domain family. All variants causing the loss or gain of a Lutheran antigen were analyzed for residue accessibility and intraprotein interactions.
An antibody to a high-prevalence antigen in the plasma of a pregnant woman was determined to be directed at a novel Lutheran antigen. Sequencing of BCAM found three homozygous changes: c.212G > A (p.Arg71His) and two silent, c.711C > T and c.714C > T. The model was built from the first two immunoglobulin crystallized domains of BCAM (D1, D2), three other templates (for D3, D4 and D5 with a higher sequence identity with the target than those used for the model proposed by Burton and Brady in 2008, and for the transmembrane region) and RaptorX (for the intracellular domain). All residues associated with a Lutheran antigen were found to be exposed in wild-type or variant proteins, except p.447 associated with loss of Lu13 expression.
The c.212G > A change results in the loss of LUGA (LU24) antigen. Whole genome sequencing continues to reveal polymorphisms with uncertain immunogenicity. This model and demonstration that nearly all residues associated with the expression of a Lutheran antigen are exposed will help evaluate the significance of new polymorphisms.
基底细胞黏附分子（BCAM）携带路德（LU，ISBT005）系统的抗原。我们报告了一种新的路德抗原，并提出了一个更新的BCAM全长三维模型。
采用标准方法进行红细胞检测、抗体鉴定和BCAM基因组DNA测序。BCAM的多模板同源建模使用了为覆盖范围、最高序列同一性和蛋白质结构域家族选择的结构模板。分析了所有导致路德抗原丢失或获得的变体的残基可及性和蛋白质内相互作用。
确定一名孕妇血浆中针对一种高频率抗原的抗体是针对一种新的路德抗原。BCAM测序发现三个纯合变化：c.212G＞A（p.Arg71His）和两个沉默变化，c.711C＞T和c.714C＞T。该模型由BCAM的前两个免疫球蛋白结晶结构域（D1、D2）、其他三个模板（用于D3、D4和D5，与目标序列的同一性高于2008年Burton和Brady提出的模型所使用的模板，以及用于跨膜区域）和RaptorX（用于细胞内结构域）构建。除了与Lu13表达缺失相关的p.447外，所有与路德抗原相关的残基在野生型或变体蛋白中均暴露。
c.212G＞A变化导致LUGA（LU24）抗原丢失。全基因组测序继续揭示具有不确定免疫原性的多态性。这个模型以及几乎所有与路德抗原表达相关的残基都暴露在外的证明将有助于评估新多态性的意义。
