Background

Per the ISHLT 2016 definition, a C4d-positive lung biopsy is required to meet criteria for definite antibody-mediated rejection (AMR). Unfortunately, C4d has poor sensitivity and specificity, and low inter-rater reliability. Phosphorylated S6 ribosomal protein (p-S6RP) expressed via the mTOR pathway has been shown to be a biomarker of AMR and correlates with donor-specific antibodies (DSA) in heart allografts. However, p-S6RP immunohistochemistry (IHC) in the setting of pulmonary AMR has yet to be evaluated. We sought to determine whether p-S6RP IHC performed on lung biopsies correlates with de novo DSA.

Methods

IHC for p-S6RP performed on 26 biopsies from lung transplant recipients with de novo HLA DSA (DSA+) and 28 biopsies from patients with no DSA (DSA-) were evaluated by 3 pathologists who independently scored the degree of alveolar macrophage and pneumocyte staining. Staining in ≥50% of the biopsy as determined by at least 2 pathologists was considered positive.

Results

Twenty-one (81%) DSA+ biopsies stained positive for p-S6RP in pneumocytes and 21 (81%) in macrophages. Six DSA- biopsies (21%) stained positive for p-S6RP in pneumocytes, 6 (21%) were positive in macrophages. Pneumocyte p-S6RP staining was 81% sensitive and 79% specific for DSA. Macrophage staining showed the same sensitivity and specificity but with lower inter-rater agreement (κ = 0.53 vs 0.68).

Conclusions

This study demonstrates a positive relationship between de novo DSA and p-S6RP expression in pneumocytes and macrophages using IHC. p-S6RP is relatively sensitive and specific, and has superior inter-rater reliability compared to C4d.

中文翻译：

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免疫组化磷酸化 S6 核糖体蛋白表达与肺同种异体移植受者的从头供体特异性 HLA 抗体相关

背景

根据 ISHLT 2016 的定义，需要 C4d 阳性肺活检才能满足明确的抗体介导排斥 (AMR) 的标准。不幸的是， C4d的敏感性和特异性较差，并且评估者间的可靠性较低。通过 mTOR 途径表达的磷酸化 S6 核糖体蛋白(p-S6RP) 已被证明是 AMR 的生物标志物，并且与心脏同种异体移植物中的供体特异性抗体 (DSA) 相关。然而，肺 AMR 中的 p-S6RP 免疫组织化学 (IHC) 尚待评估。我们试图确定对肺活检进行的 p-S6RP IHC 是否与从头 DSA 相关。

方法

3名病理学家对肺泡巨噬细胞和肺细胞染色的程度进行了独立评分，对 26 例新 HLA DSA (DSA+) 肺移植受者的活检组织和 28 例无 DSA (DSA-) 患者的活检组织进行了针对 p-S6RP 的 IHC 。由至少 2 名病理学家确定的≥50% 的活检染色被认为是阳性的。

结果

21 个 (81%) DSA+ 活检在肺细胞中 p-S6RP 染色阳性，21 个 (81%) 在巨噬细胞中染色。6 个 DSA 活检 (21%) 在肺细胞中 p-S6RP 染色呈阳性，6 个 (21%) 在巨噬细胞中呈阳性。肺细胞 p-S6RP 染色对 DSA 的敏感性为 81%，特异性为 79%。巨噬细胞染色显示出相同的敏感性和特异性，但评分者间一致性较低（κ = 0.53 vs 0.68）。

结论

该研究证明了使用 IHC 的肺细胞和巨噬细胞中的从头 DSA 和 p-S6RP 表达之间存在正相关关系。p-S6RP 相对敏感和特异，与 C4d 相比具有更好的评估者间信度。