Recognition that allograft microvascular inflammation can occur in the absence of circulating donor-specific anti-HLA antibodies (DSAs) led to the inclusion of two new categories in the diagnostic framework of the 2022 Banff Classification of Renal Allograft Pathology: ‘microvascular inflammation or injury (MVI), DSA-negative, and C4d-negative’, which includes cases of allograft rejection with no evidence of an antibody-mediated response; and ‘probable antibody-mediated rejection’, which includes DSA-positive cases with mild microvascular inflammation but without C4d deposition. New findings presented at ASN Kidney Week 2024 and published in the New England Journal of Medicine provide insights into the clinical importance of these new phenotypes. “Our study revealed distinct phenotypes of microvascular inflammation, each associated with a varying risk of disease progression and long-term graft failure,” explains researcher Alexandre Loupy. “It highlights the importance of clinically recognizing these phenotypes to standardize renal diagnostics and improve patient risk stratification and treatment.”

Assessment of long-term graft outcomes revealed that despite similar clinical features at presentation, kidney transplant recipients with evidence of microvascular inflammation according to the 2022 Banff classification had a higher risk of alloimmune-mediated disease progression and worse long-term graft survival than patients with nonrejection-related diagnoses. Specifically, patients with a diagnosis classified as MVI, DSA-negative, and C4d-negative or probable antibody-mediated rejection had a higher cumulative incidence of antibody-mediated rejection compared with patients without a diagnosis of microvascular inflammation over a median of 5-years follow-up but a lower cumulative incidence compared with patients with active antibody-mediated rejection. Likewise, the risk of development or progression of transplant glomerulopathy was similar between the two microvascular inflammation phenotypes but lower than that of patients with active antibody-mediated rejection.

认识到同种异体移植物微血管炎症可以在没有循环供体特异性抗 HLA 抗体 （DSA） 的情况下发生，因此在 2022 年班夫同种异体移植物病理分类的诊断框架中纳入了两个新类别：“微血管炎症或损伤 （MVI）、DSA 阴性和 C4d 阴性”，其中包括同种异体移植物排斥反应病例，没有抗体介导的反应证据;和“可能的抗体介导的排斥反应”，包括具有轻度微血管炎症但没有 C4d 沉积的 DSA 阳性病例。在 2024 年 ASN 肾脏周上发表并发表在《新英格兰医学杂志》上的新发现为这些新表型的临床重要性提供了见解。“我们的研究揭示了微血管炎症的不同表型，每种表型都与疾病进展和长期移植失败的不同风险有关，”研究人员 Alexandre Loupy 解释说。“它强调了临床识别这些表型对标准化肾脏诊断和改善患者风险分层和治疗的重要性。”

对长期移植物结局的评估显示，尽管就诊时具有相似的临床特征，但根据 2022 年 Banff 分类，有微血管炎症证据的肾移植受者比非排斥相关诊断的患者具有更高的免疫介导疾病进展风险和更差的长期移植物存活率。具体而言，在中位 5 年随访中，与未诊断为微血管炎症的患者相比，诊断为 MVI、DSA 阴性和 C4d 阴性或疑似抗体介导的排斥反应的患者，抗体介导的排斥反应的累积发生率更高，但与活动性抗体介导的排斥反应患者相比，累积发生率更低。同样，两种微血管炎症表型之间移植肾小球病发展或进展的风险相似，但低于活动性抗体介导的排斥反应患者。