“亚洲型”DEL表达完整D抗原的分子机制研究

D放散型（DEL）的D抗原极弱，长期被检测为D阴性，临床需预防抗-D免疫所致输血反应和溶血病。DEL在我国初筛D阴性人群中占25%，其中>90%为携带RHD*1227A等位基因的亚洲型DEL。以往报道该等位基因可导致异常剪接而无法产生正常转录本，仅形成多种外显子9缺失的异常转录本，这些异常转录本无法表达完整D抗原。但在我们超600例和其他地区493例有D阳性胎儿孕产史的亚洲型DEL孕妇中无一例产生抗-D，表明母婴D血型相合，即其表达完整D抗原，这与其未发现正常转录本相矛盾。我们从亚洲型DEL个体分离培养的前体红细胞中检出微量含外显子9的转录本。据此推测亚洲型DEL中存在传统方法无法检测的低丰度正常转录本。本研究拟通过灵敏的三代测序获得其存在低丰度正常转录本的证据，并通过体外表达阐明其表达完整D抗原的分子基础，为未来指导亚洲型DEL患者输注D阳性血和孕妇免除抗-D免疫球蛋白注射提供理论依据。

D-elute (DEL) is a very weak form of D antigen expressed on the surface of red blood cell. Clinically DEL individuals have been commonly typed and treated as D negative for a long time. DEL individuals should prevent hemolytic transfusion reactions and hemolytic disease of the fetus and newborn caused by anti-D alloimmunization. Approximately 25% of the individuals shown to be RhD-negative by conventional serological techniques in China were identified to be DEL. The RHD*1227A, which was termed “Asia type” DEL, accounted for up to 90% of the DEL phenotype in China. Previously several studies reported that a series of aberrant RHD transcripts rather than normal full-length RHD transcript were identified in the “Asia type” DEL. All of these aberrant RHD transcripts skipped exon 9 and could not express a complete repertoire of D epitopes. However, our own study with more than 600 “Asia type” DEL pregnant women cases and other studies with 493 “Asia type” DEL pregnant women cases showed that none of these “Asia type” DEL pregnant women formed alloanti-D. All of these “Asia type” DEL pregnant women had delivered RhD-positive infant. These indicate the existence of compatibility and same repertoire of D antigen between the pregnant women and the RhD positive infant, which is contradictory with the aberrant mRNA transcript result. In our previous study, very low abundance transcripts with exon 9 were identified from the cultured erythroblast from the “Asia type” DEL individuals. Based on this data, we speculated that very low number of complete repertoire of D antigens of “Asia type” DEL were expressed by low abundant of normal full-length RHD mRNA transcripts, D antigens on the surface of red blood cell were too few to be detected by the routine methods used in previous studies. In this study, third generation sequencing technology, which is more sensitive, will be used to confirm whether normal full-length RHD transcript exists in “Asia type” DEL. In addition, expression studies in vitro will be conducted to clarify the molecular basis for expression of complete repertoire of D epitopes in “Asia type” DEL. This study will provide the basic theoretical evidence for the establishment of specific strategy about transfusion and pregnancy for “Asia type” DEL patients in the future.