Wei Ling, Zhu Siying, Wen Jizhi, Liao Zhijian, Jia Shuangshuang, Ji Yanli
Institute of Blood Transfusion and Hematology, Guangzhou Blood Center, Guangzhou Medical University, Guangzhou, China.
The Key Medical Laboratory of Guangzhou, Guangzhou, China.
Blood Transfus. 2025 Jul-Aug;23(4):357-364. doi: 10.2450/BloodTransfus.1003. Epub 2025 May 14.
The s antigen expression is mainly determined by a single nucleotide polymorphism at c.143C (p.Thr48) on the exon 4 of GYPB gene. Several mutations on the GYPB gene have been reported to cause aberrant s antigen expression. GP.Mur has an extra 31-amino acid insertion encoded by the active compound GYP(B-A) exon 3, which closely locates at the upstream of p.Thr48. It has been reported to cause altered s antigen expression.
Serologic testing and flow cytometry analysis were performed to detect s antigen expression on RBCs of GP(B-A-B) hybrid glycophorins, including GP.Mur, GP.Bun and GP.HF. Several mutant plasmids based on the different sites between GYPB and GYP(B-A-B) alleles were constructed and transfected into HEK293T cells for in vitro expression, to reveal the key amino acids for the aberrant s antigen expression.
Serologic testing and flow cytometry assay showed the RBCs of GP.Mur homozygotes reacted positively with IgG anti-s (P3YAN3) but negatively with IgM anti-s (P3BER). Flow cytometry analysis also revealed half level of s antigen expressed on the RBCs of GP.Mur, GP.Bun and GP.HF heterozygotes with ss genotype compared to S-s+ controls when detected by IgM anti-s (P3BER). Furthermore, in vitro expression study showed that p.Asn45 is critical for the epitope expression of s antigen detected by IgM anti-s (P3BER).
The results demonstrated partial s antigen expression on GP(B-A-B) RBCs. In addition to p.Thr48, p.Asn45 is also important for the epitope expression of s antigen detected by IgM anti-s (P3BER). To avoid false negative serologic typing, it is recommended to use several different clones of monoclonal anti-s for the correct s typing, especially in the regions with high frequency distribution of GP(B-A-B) hybrid glycophorins.
s抗原的表达主要由GYPB基因第4外显子c.143C（p.Thr48）处的单核苷酸多态性决定。据报道，GYPB基因上的几种突变会导致s抗原表达异常。GP.Mur具有由活性化合物GYP（B-A）外显子3编码的额外31个氨基酸插入，其紧邻p.Thr48的上游。据报道，它会导致s抗原表达改变。
进行血清学检测和流式细胞术分析，以检测包括GP.Mur、GP.Bun和GP.HF在内的GP（B-A-B）杂合糖蛋白红细胞上的s抗原表达。构建了基于GYPB和GYP（B-A-B）等位基因之间不同位点的几种突变质粒，并转染到HEK293T细胞中进行体外表达，以揭示s抗原表达异常的关键氨基酸。
血清学检测和流式细胞术分析显示，GP.Mur纯合子的红细胞与IgG抗s（P3YAN3）反应呈阳性，但与IgM抗s（P3BER）反应呈阴性。流式细胞术分析还显示，当用IgM抗s（P3BER）检测时，与S-s+对照相比，GP.Mur、GP.Bun和GP.HF杂合子（ss基因型）红细胞上表达的s抗原水平为一半。此外，体外表达研究表明，p.Asn45对于IgM抗s（P3BER）检测的s抗原表位表达至关重要。
结果表明GP（B-A-B）红细胞上存在部分s抗原表达。除了p.Thr48外，p.Asn45对于IgM抗s（P3BER）检测的s抗原表位表达也很重要。为避免血清学分型出现假阴性，建议使用几种不同克隆的单克隆抗s进行正确的s分型，尤其是在GP（B-A-B）杂合糖蛋白高频分布的地区。
