Supplementary Material for: GDF15 Suppresses Lymphoproliferation and Humoral Autoimmunity in a Murine Model of Systemic Lupus Erythematosus

Growth and differentiation factor 15 (GDF15), a divergent member of the transforming growth factor-β superfamily, has been associated with acute and chronic inflammatory conditions including autoimmune disease, i.e., type I diabetes and rheumatoid arthritis. Still, its role in systemic autoimmune disease remains elusive. Thus, we studied GDF15-deficient animals in Fas-receptor intact (C57BL/6) or deficient (C57BL/6^{<i>lpr/lpr</i>}) backgrounds. Further, lupus nephritis (LN) microdissected kidney biopsy specimens were analyzed to assess the involvement of GDF15 in human disease. GDF15-deficiency in lupus-prone mice promoted lymphoproliferation, T-, B- and plasma cell-expansion, a type I interferon signature, and increased serum levels of anti-DNA autoantibodies. Accelerated systemic inflammation was found in association with a relatively mild renal phenotype. Splenocytes of phenotypically overall-normal <i>Gdf15−/−</i> C57BL/6 and lupus-prone C57BL/6^{<i>lpr/lpr</i>} mice displayed increased in vitro lymphoproliferative responses or interferon-dependent transcription factor induction in response to the toll-like-receptor (TLR)-9 ligand CpG, or the TLR-7 ligand Imiquimod, respectively. In human LN, GDF15 expression was downregulated whereas type I interferon expression was upregulated in glomerular- and tubular-compartments versus living donor controls. These findings demonstrate that GDF15 regulates lupus-like autoimmunity by suppressing lymphocyte-proliferation and -activation. Further, the data indicate a negative regulatory role for GDF15 on TLR-7 and -9 driven type I interferon signaling in effector cells of the innate immune system.

生长分化因子15（GDF15）作为转化生长因子-β超家族的一个异型成员，已被证实与包括自身免疫病在内的急慢性炎症性疾病相关，例如1型糖尿病与类风湿关节炎。然而，其在系统性自身免疫病中的作用仍未明确。为此，本研究在Fas受体完整（C57BL/6）或缺陷（C57BL/6^{<i>lpr/lpr</i>}）的遗传背景下，对GDF15基因敲除动物进行了研究。此外，我们还对显微切割获取的狼疮肾炎（LN）肾活检标本进行分析，以评估GDF15在人类疾病中的参与作用。在狼疮易感小鼠中，GDF15基因敲除可促进淋巴增殖、T细胞、B细胞及浆细胞扩增，诱导I型干扰素特征，并升高血清抗DNA自身抗体水平。同时可观察到加速的全身炎症反应，伴随相对较轻的肾脏表型。表型整体正常的Gdf15^−/− C57BL/6小鼠与狼疮易感的C57BL/6^{<i>lpr/lpr</i>}小鼠的脾细胞，分别在受到toll样受体（TLR）9配体CpG或TLR7配体咪喹莫特刺激时，表现出增强的体外淋巴增殖反应或干扰素依赖的转录因子激活。在人类狼疮肾炎样本中，与活体供体对照组相比，肾小球与肾小管区域的GDF15表达下调，而I型干扰素表达则显著上调。上述研究结果表明，GDF15可通过抑制淋巴细胞增殖与活化，调控狼疮样自身免疫反应。此外，本研究数据提示，GDF15在先天免疫系统效应细胞中，对TLR7与TLR9介导的I型干扰素信号通路发挥负向调控作用。