Zand Ladan, Russo Ilario, Vargas-Brochero Maria J, Nasr Samih H, Madden Benjamin, Theis Jason D, Fervenza Fernando C, Sethi Sanjeev
Division of Nephrology and Hypertension, Mayo Clinic, Rochester, Minnesota, USA.
Division of Nephrology and Hypertension, Mayo Clinic, Rochester, Minnesota, USA; Department of Precision and Regenerative Medicine and Ionian Area (DIMEPRE-J), University of Bari Aldo Moro, Bari, Italy.
Kidney Int. 2025 Jun 6. doi: 10.1016/j.kint.2025.04.032.
Membranous nephropathy (MN) is characterized by subepithelial deposition of immune complexes along the glomerular basement membrane. The muscle-type phospholipase A2 receptor (PLA2R) has been identified as the principal antigen in MN, and its detection via immunofluorescence (IF) studies remains a diagnostic cornerstone. Advancements, including laser microdissection/mass spectrometry (LMD/MS), offer enhanced sensitivity for antigen identification, independent of epitope accessibility.
A cohort of 250 kidney biopsy samples (discovery cohort) diagnosed as PLA2R-negative MN by IF underwent LMD/MS analysis for antigen detection. Biopsies were microdissected, and peptides were analyzed using high-performance liquid chromatography coupled with mass spectrometry. Total spectral counts greater than 10 are considered positive for PLA2R-associated MN.
LMD/MS identified PLA2R antigen in seven (2.8%) cases classified as PLA2R-negative by IF. The mean total spectral count in the seven cases was 55. Additionally, LMD/MS detected another two positive cases in PLA2R-negative MN from a recently validated clinical test for antigen detection. The mean total spectral count in these two cases was 189. All nine cases showed significant IgG along the glomerular basement membrane. Electron microscopy showed stage II MN in seven of the nine cases, one case showed stage I, and the other showed stage III-IV MN. Serologic studies showed anti-PLA2R antibodies in two of seven cases with available data.
A small subset of PLA2R-negative MN by IF became PLA2R-positive by LMD/MS. Our study emphasizes the importance of not ruling out the possibility of PLA2R-associated MN in patients with negative IF staining for PLA2R. LMD/MS is an important diagnostic test for MN antigen detection.
膜性肾病（MN）的特征是免疫复合物沿肾小球基底膜上皮下沉积。肌肉型磷脂酶A2受体（PLA2R）已被确定为MN中的主要抗原，通过免疫荧光（IF）研究对其进行检测仍然是诊断的基石。包括激光显微切割/质谱（LMD/MS）在内的技术进步，提高了抗原鉴定（独立于表位可及性）的灵敏度。
对250例经IF诊断为PLA2R阴性MN的肾活检样本（发现队列）进行LMD/MS分析以检测抗原。对活检样本进行显微切割，使用高效液相色谱与质谱联用分析肽段。总光谱计数大于10被认为PLA2R相关MN呈阳性。
LMD/MS在7例（2.8%）经IF分类为PLA2R阴性的病例中鉴定出PLA2R抗原。这7例病例的平均总光谱计数为55。此外，在一项最近经验证的抗原检测临床测试中，LMD/MS在PLA2R阴性MN中又检测到另外2例阳性病例。这2例病例的平均总光谱计数为189。所有9例病例在肾小球基底膜均显示显著的IgG。电子显微镜检查显示，9例病例中有7例为II期MN，1例为I期，另1例为III-IV期MN。血清学研究显示，7例有可用数据的病例中有2例存在抗PLA2R抗体。
一小部分IF检测为PLA-2R阴性的MN经LMD/MS检测变为PLA2R阳性。我们的研究强调了在PLA2R的IF染色为阴性的患者中不排除PLA2R相关MN可能性的重要性。LMD/MS是MN抗原检测的一项重要诊断测试。
