Luo Qizhi, Yin Xiangli, Zhu Quan, Luo Weiguang, Liu Rongjiao, Wei Leiyan, Zou Yizhou
Department of Immunology, School of Xiangya Basic Medical Sciences, Central South University, Changsha, China.
Front Immunol. 2025 May 19;16:1563872. doi: 10.3389/fimmu.2025.1563872. eCollection 2025.
The major histocompatibility complex class I-related gene A (), is a highly polymorphic gene, serve as a crucial role in immune regulator through its interaction with the NKG2D receptor on natural killer (NK) cells. These polymorphisms may influence immune responses, disease susceptibility, and transplant outcomes. However, the precise mechanisms by which polymorphisms modulate NKG2D receptor activation remain poorly understood.
We analyzed 29 representative MICA polymorphic molecules that cover the most prevalent alleles in the population. These variants were systematically examined through Luminex bead assays, monoclonal antibody binding studies, and NKG2D-Ig fusion protein assays. NKG2D receptor activation was assessed using NKG2D reporter cells, while NK cell-mediated cytotoxicity was evaluated through NKL cell killing assays against target cells expressing either Type-I or Type-II MICA molecules.
Our analysis identified two major types of polymorphisms based on antigenic epitopes and NKG2D binding characteristics. Type-I MICA characterized by six specific polymorphic site and their associated amino acid variants. exhibited significantly stronger NKG2D receptor binding affinity and more robust receptor activation compared to Type-II polymorphisms. This functional distinction was further corroborated by enhanced NK cells cytotoxicity against target cells expressing Type-I MICA molecules. Importantly, these differences in receptor activation and NK cell killing efficiency were attributable to six critical polymorphic amino acid sites.
This study demonstrates the existence of two distinct types of polymorphisms that differentially regulate NKG2D receptor activation and NK cell cytotoxicity. These findings offer new insights into that how genetic variation in MICA may contribute to individual differences in disease susceptibility through immune regulation mechanisms.
主要组织相容性复合体I类相关基因A（MICA）是一个高度多态的基因，通过与自然杀伤（NK）细胞上的NKG2D受体相互作用，在免疫调节中发挥关键作用。这些多态性可能影响免疫反应、疾病易感性和移植结果。然而，MICA多态性调节NKG2D受体激活的确切机制仍知之甚少。
我们分析了29个代表性的MICA多态分子，这些分子涵盖了人群中最常见的等位基因。通过Luminex微球分析、单克隆抗体结合研究和NKG2D-Ig融合蛋白分析对这些变体进行了系统研究。使用NKG2D报告细胞评估NKG2D受体激活，同时通过针对表达I型或II型MICA分子的靶细胞的NKL细胞杀伤试验评估NK细胞介导的细胞毒性。
我们的分析基于抗原表位和NKG2D结合特征确定了两种主要类型的MICA多态性。I型MICA的特征是六个特定的多态性位点及其相关的氨基酸变体。与II型多态性相比，I型MICA表现出显著更强的NKG2D受体结合亲和力和更强大的受体激活。对表达I型MICA分子的靶细胞的NK细胞细胞毒性增强进一步证实了这种功能差异。重要的是，受体激活和NK细胞杀伤效率的这些差异归因于六个关键的多态性氨基酸位点。
本研究证明存在两种不同类型的MICA多态性，它们对NKG2D受体激活和NK细胞细胞毒性有不同的调节作用。这些发现为MICA基因变异如何通过免疫调节机制导致疾病易感性的个体差异提供了新的见解。
