Reefman Esther, Horst Gerda, Nijk Marije T, Limburg Pieter C, Kallenberg Cees G M, Bijl Marc
University Medical Center Groningen, and University of Groningen, Groningen, The Netherlands.
Arthritis Rheum. 2007 Oct;56(10):3399-411. doi: 10.1002/art.22947.
Decreased clearance of apoptotic cells is suggested to be a major pathogenic factor in systemic lupus erythematosus (SLE). The aim of this study was to investigate whether the binding of SLE autoantibodies to apoptotic cells influences the phagocytosis of these cells by macrophages.
Apoptosis was induced in a human T cell line (Jurkat) and a keratinocyte cell line (HaCaT) by ultraviolet B irradiation. Binding of purified IgG from 26 SLE patients and 15 healthy controls to apoptotic cells was assessed by flow cytometry and Western blotting. Phagocytosis of IgG-opsonized apoptotic cells by monocyte-derived macrophages was assessed by light microscopy. Similar experiments were performed with a monoclonal antibody against SSA/Ro and IgG fractions from 5 patients with Sjögren's syndrome (SS) and 5 patients with rheumatoid arthritis (RA).
IgG fractions from all 26 SLE patients bound to late apoptotic, but not early apoptotic, cells. IgG fractions isolated from SLE patients with different autoantibody profiles showed comparable levels of binding. IgG fractions from healthy controls did not bind. Opsonization of apoptotic cells with IgG fractions from SLE patients resulted in a significant inhibition of phagocytosis as compared with healthy control IgG fractions. A monoclonal antibody directed against SSA/Ro and IgG isolated from 5 antinuclear antibody (ANA)-positive patients with SS were also able to elicit these effects, whereas IgG from 5 ANA-negative patients with RA did not. The inhibitory effect of patient IgG was abolished by blocking either the Fcgamma receptors (FcgammaR) or the constant region of IgG, using a specific Fc-blocking peptide.
Autoantibodies from SLE patients are able to opsonize apoptotic cells and inhibit their uptake by macrophages via an FcgammaR-dependent mechanism.
凋亡细胞清除率降低被认为是系统性红斑狼疮（SLE）的主要致病因素。本研究旨在探讨SLE自身抗体与凋亡细胞的结合是否会影响巨噬细胞对这些细胞的吞噬作用。
通过紫外线B照射诱导人T细胞系（Jurkat）和角质形成细胞系（HaCaT）发生凋亡。采用流式细胞术和蛋白质印迹法评估26例SLE患者和15例健康对照者的纯化IgG与凋亡细胞的结合情况。通过光学显微镜评估单核细胞来源的巨噬细胞对IgG调理的凋亡细胞的吞噬作用。使用抗SSA/Ro单克隆抗体以及来自5例干燥综合征（SS）患者和5例类风湿关节炎（RA）患者的IgG组分进行了类似实验。
所有26例SLE患者的IgG组分均与晚期凋亡细胞结合，但不与早期凋亡细胞结合。从具有不同自身抗体谱的SLE患者中分离出的IgG组分显示出相当的结合水平。健康对照者的IgG组分未结合。与健康对照者的IgG组分相比，SLE患者的IgG组分调理凋亡细胞导致吞噬作用显著受到抑制。从5例抗核抗体（ANA）阳性的SS患者中分离出的抗SSA/Ro单克隆抗体和IgG也能够引发这些效应，而来自5例ANA阴性的RA患者的IgG则不能。使用特异性Fc阻断肽阻断Fcγ受体（FcγR）或IgG的恒定区可消除患者IgG的抑制作用。
SLE患者的自身抗体能够调理凋亡细胞，并通过FcγR依赖机制抑制巨噬细胞对其摄取。
