The DEL phenotype represents an intriguing and challenging aspect of blood group serology. This condition is characterized by an extremely weak expression of the D antigen on red blood cells, to the extent that it often eludes detection through routine serological methods. Identifying the DEL phenotype necessitates more specialized techniques, such as adsorption and elution tests, to reveal the presence of the D antigen. This distinctive phenotype underscores the complexity and subtlety of blood group genetics and highlights the importance of using advanced methods to accurately classify individuals with this condition, as their ability to form anti-D antibodies can have clinical implications during transfusion and pregnancy scenarios. There is a paucity of data for the DEL phenotype in the Indian population, and the molecular basis has not been elucidated yet. Our investigation delves into the genetic underpinnings of two distinct DEL phenotype cases that pose challenges for resolution through conventional serological techniques. We employ next-generation amplicon sequencing to unravel the intricate genetic landscape underlying these cases. In the D-negative donor, the DEL phenotype was first identified serologically, which was subsequently confirmed by molecular analysis. In the second case, it was associated with an anti-D antibody in a D-positive patient. Initial data analysis unveiled a substantial reduction in coverage across the exonic segments of the RHD gene in both samples, suggesting the potential presence of RHD exon deletions. On both occasions, we identified a homozygous intronic RHD polymorphism that is well established to be linked to the RHD* 01EL.32/RHD*DEL32 variant.

中文翻译：

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印度人群 DEL 表型的分子基础：二代测序分析的见解

DEL 表型代表了血型血清学的一个有趣且具有挑战性的方面。这种情况的特点是红细胞上 D 抗原的表达极弱，以至于经常无法通过常规血清学方法检测到。识别 DEL 表型需要更专门的技术，例如吸附和洗脱测试，以揭示 D 抗原的存在。这种独特的表型强调了血型遗传学的复杂性和微妙性，并强调了使用先进方法对患有这种疾病的个体进行准确分类的重要性，因为它们形成抗 D 抗体的能力可能在输血和怀孕情况下具有临床意义。印度人群中 DEL 表型的数据很少，其分子基础尚未阐明。我们的研究深入研究了两种不同 DEL 表型病例的遗传基础，这对通过传统血清学技术解决问题提出了挑战。我们采用下一代扩增子测序来揭示这些病例背后复杂的遗传图谱。在 D 阴性供体中，DEL 表型首先通过血清学方法鉴定，随后通过分子分析得到证实。在第二种情况下，它与 D 阳性患者体内的抗 D 抗体有关。初步数据分析显示，两个样本中 RHD 基因外显子片段的覆盖范围大幅减少，表明可能存在 RHD 外显子缺失。在这两种情况下，我们都鉴定出了纯合内含子 RHD 多态性，该多态性已被证实与 RHD* 01EL.32/RHD*DEL32 变体相关。