Papazahariadou M, Athanasiadis G I, Papadopoulos E, Symeonidou I, Hatzistilianou M, Castellani M L, Bhattacharya K, Shanmugham L N, Conti P, Frydas S
Laboratory of Parasitology, Veterinary Faculty, Aristotele University, Thessaloniki, Greece.
Int J Biol Markers. 2007 Apr-Jun;22(2):144-53. doi: 10.1177/172460080702200208.
Host resistance against pathogens depends on a complex interplay of innate and adaptive immune mechanisms. Acting as an early line of defence, the immune system includes activation of neutrophils, tissue macrophages, monocytes, dendritic cells, eosinophils and natural killer (NK) cells. NK cells are lymphoid cells that can be activated without previous stimulation and are therefore like macrophages in the first line of defence against tumor cells and a diverse range of pathogens. NK cells mediate significant activity and produce high levels of proinflammatory cytokines in response to infection. Their cytotoxicity production is induced principally by monocyte-, macrophage- and dendritic cell-derived cytokines, but their activation is also believed to be cytokine-mediated. Recognition of infection by NK cells is accomplished by numerous activating and inhibitory receptors on the NK cells' surface that selectively trigger the cytolytic activity in a major histocompability complex-independent manner. NK cells have trypanocidal activity of fibroblast cells and mediate direct destruction of extracellular epimastigote and trypomastigote forms of T. cruzi and T. lewisi in vitro; moreover, they kill plasmodia-infected erythrocytes directly through cell-cell interaction. This review provides a more detailed analysis of how NK cells recognize and respond to parasites and how they mediate cytotoxicity against tumor cells. Also the unique role of NK cells in innate immunity to infection and the relationship between parasites and carcinogenesis are discussed.
宿主对病原体的抵抗力取决于先天性和适应性免疫机制的复杂相互作用。作为早期防御线，免疫系统包括中性粒细胞、组织巨噬细胞、单核细胞、树突状细胞、嗜酸性粒细胞和自然杀伤（NK）细胞的激活。NK细胞是淋巴细胞，无需预先刺激即可被激活，因此在抵御肿瘤细胞和多种病原体的第一道防线中类似于巨噬细胞。NK细胞介导显著的活性，并在感染时产生高水平的促炎细胞因子。它们的细胞毒性产生主要由单核细胞、巨噬细胞和树突状细胞衍生的细胞因子诱导，但它们的激活也被认为是由细胞因子介导的。NK细胞对感染的识别是通过NK细胞表面的众多激活和抑制受体来完成的，这些受体以主要组织相容性复合体非依赖的方式选择性地触发细胞溶解活性。NK细胞对成纤维细胞具有杀锥虫活性，并在体外介导对克氏锥虫和路易斯锥虫细胞外上鞭毛体和锥鞭毛体形式的直接破坏；此外，它们通过细胞间相互作用直接杀死疟原虫感染的红细胞。本综述对NK细胞如何识别和应对寄生虫以及它们如何介导对肿瘤细胞的细胞毒性进行了更详细的分析。还讨论了NK细胞在先天性感染免疫中的独特作用以及寄生虫与致癌作用之间的关系。
