Wuhrer Manfred, Selman Maurice H J, McDonnell Liam A, Kümpfel Tania, Derfuss Tobias, Khademi Mohsen, Olsson Tomas, Hohlfeld Reinhard, Meinl Edgar, Krumbholz Markus
Center for Proteomics and Metabolomics, Leiden University Medical Center, Leiden, The Netherlands.
Department of Molecular Cell Biology and Immunology, VU University Medical Center, Amsterdam, The Netherlands.
J Neuroinflammation. 2015 Dec 18;12:235. doi: 10.1186/s12974-015-0450-1.
Immunoglobulin G (IgG) effector functions are regulated by the composition of glycans attached to a conserved N-glycosylation site in the Fc part. Intrathecal production of IgG, especially IgG1, is a hallmark of multiple sclerosis (MS), but nothing is known about IgG Fc glycosylation in MS and in cerebrospinal fluid (CSF) in general.
We applied mass spectrometry of tryptic Fc glycopeptides to analyze IgG Fc glycosylation (sialylation, galactosylation, fucosylation, and bisecting N-acetylglucosamine (GlcNAc)) in 48 paired CSF and serum samples from adult patients with MS or a first demyelinating event highly suggestive of MS (designated as MS cases), and from healthy volunteers and patients with other non-inflammatory diseases (control group). p values were adjusted for multiple testing.
Our experiments revealed four main results. First, IgG1 glycosylation patterns were different in CSF vs. serum, in the MS group and even in control donors without intrathecal IgG synthesis. Second, in MS patients vs. controls, IgG1 glycosylation patterns were altered in CSF, but not in serum. Specifically, in CSF from the MS group, bisecting GlcNAc were elevated, and afucosylation and galactosylation were reduced. Elevated bisecting GlcNAc and reduced galactosylation are known to enhance IgG effector functions. Third, hypothesis-free regression analysis revealed that alterations of afucosylation and bisecting GlcNAc in CSF from MS cases peaked 2-3 months after the last relapse. Fourth, CSF IgG1 glycosylation correlated with the degree of intrathecal IgG synthesis and CSF cell count.
The CNS compartment as well as the inflammatory milieu in MS affect IgG1 Fc glycosylation. In MS, the CSF IgG1 glycosylation has features that enhance Fc effector functions.
免疫球蛋白G（IgG）的效应功能由附着于Fc部分保守N - 糖基化位点的聚糖组成所调节。鞘内产生IgG，尤其是IgG1，是多发性硬化症（MS）的一个标志，但总体而言，关于MS患者以及脑脊液（CSF）中IgG Fc糖基化情况尚无了解。
我们应用胰蛋白酶消化的Fc糖肽质谱分析法，分析了48对来自成年MS患者或高度提示MS的首次脱髓鞘事件患者（称为MS病例）、健康志愿者以及其他非炎性疾病患者（对照组）的脑脊液和血清样本中的IgG Fc糖基化（唾液酸化、半乳糖基化、岩藻糖基化和平分型N - 乙酰葡糖胺（GlcNAc））情况。对p值进行多重检验校正。
我们的实验揭示了四个主要结果。第一，在MS组中，甚至在无鞘内IgG合成的对照供体中，脑脊液与血清中的IgG1糖基化模式不同。第二，与对照组相比，MS患者脑脊液中的IgG1糖基化模式发生改变，但血清中未改变。具体而言，在MS组的脑脊液中，平分型GlcNAc升高，去岩藻糖基化和半乳糖基化降低。已知平分型GlcNAc升高和半乳糖基化降低会增强IgG效应功能。第三，无假设回归分析显示，MS病例脑脊液中去岩藻糖基化和平分型GlcNAc的改变在最后一次复发后2 - 3个月达到峰值。第四，脑脊液IgG1糖基化与鞘内IgG合成程度和脑脊液细胞计数相关。
MS中的中枢神经系统区域以及炎性环境会影响IgG1 Fc糖基化。在MS中，脑脊液IgG1糖基化具有增强Fc效应功能的特征。
