Dalpke Alexander, Heeg Klaus, Bartz Holger, Baetz Andrea
Department of Hygiene and Medical Microbiology, Institute of Hygiene, University of Heidelberg, Im Neuenheimer Feld 324, 69120 Heidelberg, Germany.
Immunobiology. 2008;213(3-4):225-35. doi: 10.1016/j.imbio.2007.10.008. Epub 2007 Nov 28.
Innate immunity represents the first line of defense against invading pathogens. Toll-like receptors (TLRs) are important for activation of innate immunity. Moreover, cytokines mediate communication of cells and are necessary to mount an appropriately regulated immune response. However, activation of innate immunity has to be tightly controlled to avoid overshooting immune reactions. Suppressor of cytokine signaling (SOCS) proteins have been identified as inducible feedback inhibitors of cytokine receptors and have been shown to be of crucial importance for the limitation of inflammatory responses. In this review, we describe the role of SOCS proteins in macrophages and dendritic cells (DCs). Based on our own findings, we show that SOCS proteins are directly induced by stimulation of TLRs. However, SOCS proteins do not interfere with direct TLR signaling, but avoid overshooting activation by regulating paracrine IFN-beta signaling. In addition, SOCS proteins in macrophages and DCs regulate the sensitivity towards IFN-gamma and GM-CSF, thereby modulating anti-microbial activity of macrophages and differentiation of DCs. We discuss that SOCS induction can also be used by microbes to evade immune defense, and this is exemplified by the parasite Toxoplasma gondii which induces SOCS1 to inhibit IFN-gamma-mediated macrophage activation. Taken together, the findings indicate that SOCS proteins play an important role in the balanced activation of innate immunity during infectious encounter.
固有免疫是抵御入侵病原体的第一道防线。Toll样受体(TLR)对于固有免疫的激活至关重要。此外,细胞因子介导细胞间通讯,是产生适当调节的免疫反应所必需的。然而,固有免疫的激活必须受到严格控制,以避免免疫反应过度。细胞因子信号转导抑制因子(SOCS)蛋白已被确定为细胞因子受体的诱导性反馈抑制剂,并已证明对限制炎症反应至关重要。在本综述中,我们描述了SOCS蛋白在巨噬细胞和树突状细胞(DC)中的作用。基于我们自己的发现,我们表明SOCS蛋白是由TLR刺激直接诱导的。然而,SOCS蛋白并不干扰TLR直接信号传导,而是通过调节旁分泌IFN-β信号传导来避免过度激活。此外,巨噬细胞和DC中的SOCS蛋白调节对IFN-γ和GM-CSF的敏感性,从而调节巨噬细胞的抗菌活性和DC的分化。我们讨论了微生物也可利用SOCS诱导来逃避免疫防御,寄生虫弓形虫诱导SOCS1抑制IFN-γ介导的巨噬细胞激活就是一个例子。综上所述,这些发现表明SOCS蛋白在感染过程中固有免疫的平衡激活中发挥重要作用。