Department of Nephrology, Peking University Third Hospital, Beijing 100191, P.R. China.
Department of Immunology, School of Basic Medical Sciences, Peking University, Beijing 100191, P.R. China.
Mol Med Rep. 2021 May;23(5). doi: 10.3892/mmr.2021.11966. Epub 2021 Mar 24.
Proximal tubular epithelial cells (PTECs) have innate immune characteristics, and produce proinflammatory factors, chemokines and complement components that drive epithelial‑mesenchymal transition (EMT). Our previous studies revealed that human mesangial cells and podocytes were able to synthesize and secrete immunoglobulin (Ig)A and IgG, respectively. The aim of the present study was to evaluate the expression of Igs in PTECs. Firstly, IgG was detected in the cytoplasm, the cell membrane and the lumen of PTECs in the normal renal cortex by immunohistochemistry. Secondly, Igγ gene transcription and V(D)J recombination were detected in single PTECs by nested PCR and Sanger sequencing. Thirdly, Igγ, Igκ and Igλ were clearly detected in an immortalized PTEC line (HK‑2) by immunostaining and western blotting, in which RP215 (an antibody that predominantly binds to non‑B cell‑derived IgG) was used. In addition, Igγ, Igκ and Igλ gene transcripts, conservative V(D)J recombination in the Igγ variable region, recombination activating gene 1/2 and activation‑induced cytidine deaminase were all detected in HK‑2 cells. These data suggested that PTECs may express IgG in a similar manner to B cells. Furthermore, IgG expression was upregulated by TGF‑β1 and may be involved in EMT.
近端肾小管上皮细胞 (PTECs) 具有先天免疫特性，并产生促炎因子、趋化因子和补体成分，从而驱动上皮-间充质转化 (EMT)。我们之前的研究表明，人肾小球系膜细胞和足细胞分别能够合成和分泌免疫球蛋白 (Ig)A 和 IgG。本研究旨在评估 Ig 在 PTECs 中的表达。首先，通过免疫组织化学检测到正常肾皮质中 PTECs 的细胞质、细胞膜和管腔中存在 IgG。其次，通过巢式 PCR 和 Sanger 测序检测到单个 PTECs 中的 Igγ 基因转录和 V(D)J 重组。第三，通过免疫染色和 Western blot 在永生化的 PTEC 系 (HK-2) 中清楚地检测到 Igγ、Igκ 和 Igλ，其中使用了 RP215（一种主要与非 B 细胞衍生的 IgG 结合的抗体）。此外，在 HK-2 细胞中还检测到了 Igγ、Igκ 和 Igλ 基因转录物、Igγ 可变区保守的 V(D)J 重组、重组激活基因 1/2 和激活诱导胞苷脱氨酶。这些数据表明，PTECs 可能以类似于 B 细胞的方式表达 IgG。此外，TGF-β1 可上调 IgG 表达，并可能参与 EMT。
