C4d在IgA肾病中的生物标志物价值:激活机制、风险分层与预后评估

The biomarker value of C4d in IgA nephropathy: activation mechanisms, risk stratification, and prognosis assessment

摘要

IgA肾病(IgAN)是常见的原发性肾小球肾炎,临床与病理进展异质性强,部分患者可进展至终末期肾病。补体系统异常激活,尤其是凝集素途径与替代途径的协同作用,在IgAN发生发展中发挥关键作用。C4d是补体C4裂解后的稳定产物,其肾组织沉积可作为补体激活的“分子足迹”,与病理损伤、蛋白尿及不良肾结局密切相关,可用于风险分层。尿液C4d作为无创指标亦可反映肾内补体激活状态,并与疾病活动度、病理严重程度及长期预后相关。C4d检测有望用于分层管理与疗效监测,但仍需标准化检测流程与阈值,并通过大样本前瞻性研究进一步验证。本文就C4d在IgAN中的激活机制、作为病理及无创生物标志物的价值与局限性进行综述,展望其临床转化前景。

Abstract

IgA nephropathy (IgAN) is a common primary glomerulonephritis characterized by marked heterogeneity in clinical and pathological progression, with a subset of patients progressing to end-stage kidney disease. Abnormal complement activation, particularly the synergistic interplay between the lectin and alternative pathways, plays a pivotal role in the pathogenesis and progression of IgAN. C4d, a stable cleavage product of complement C4, serves as a "molecular footprint" of complement activation when deposited in renal tissue, and is closely associated with pathological injury, proteinuria, and adverse renal outcomes, thus enabling risk stratification. Urinary C4d, as a non-invasive biomarker, can also reflect intrarenal complement activation status and correlates with disease activity, histologic severity, and long-term prognosis. C4d testing holds promise for stratified management and therapeutic monitoring; however, standardization of assay protocols and cut-off values, along with further validation through large-scale prospective studies, are still required. This article reviews the activation mechanisms of C4d in IgAN, its value and limitations as both a tissue and non-invasive biomarker, and discusses its prospects for clinical translation.

关键词

IgA肾病 / C4d / 补体系统 / 凝集素途径 / 替代途径 / 肾组织沉积 / 无创生物标志物 / 风险分层 / 临床预后

Key words

IgA nephropathy / C4d / Complement system / Lectin pathway / Alternative pathway / Renal tissue deposition / Non-invasive biomarkers / Risk stratification / Prognosis

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