Gazzinelli R T, Talvani A, Camargo M M, Santiago H C, Oliveira M A, Vieira L Q, Martins G A, Aliberti J C, Silva J S
Departamento de Bioquímica e Imunologia, Universidade Federal de Minas Gerais, Belo Horizonte, Brasil.
Braz J Med Biol Res. 1998 Jan;31(1):89-104. doi: 10.1590/s0100-879x1998000100012.
Toxoplasma gondii and Trypanosoma cruzi are intracellular parasites which, as part of their life cycle, induce a potent cell-mediated immunity (CMI) maintained by Th1 lymphocytes and IFN-gamma. In both cases, induction of a strong CMI is thought to protect the host against rapid parasite multiplication and consequent pathology and lethality during the acute phase of infection. However, the parasitic infection is not eliminated by the immune system and the vertebrate host serve as a parasite reservoir. In contrast, Leishmania sp, which is a slow growing parasite, appears to evade induction of CMI during early stages of infection as a strategy for surviving in a hostile environment (i.e., inside the macrophages which are their obligatory niche in the vertebrate host). Recent reports show that the initiation of IL-12 synthesis by macrophages during these parasitic infections is a key event in regulating CMI and disease outcome. The studies reviewed here indicate that activation/inhibition of distinct signaling pathways and certain macrophage functions by intracellular protozoa are important events in inducing/modulating the immune response of their vertebrate hosts, allowing parasite and host survival and therefore maintaining parasite life cycles.
刚地弓形虫和克氏锥虫是细胞内寄生虫，在其生命周期中，它们会诱导由Th1淋巴细胞和干扰素-γ维持的强大细胞介导免疫（CMI）。在这两种情况下，诱导强烈的CMI被认为可保护宿主免受寄生虫在感染急性期快速增殖以及随之而来的病理变化和致死性的影响。然而，免疫系统并不能消除寄生虫感染，脊椎动物宿主成为了寄生虫的储存库。相比之下，利什曼原虫属是一种生长缓慢的寄生虫，在感染早期似乎会逃避CMI的诱导，以此作为在恶劣环境（即巨噬细胞内，巨噬细胞是它们在脊椎动物宿主体内的必居之地）中存活的一种策略。最近的报告表明，在这些寄生虫感染期间巨噬细胞启动白细胞介素-12的合成是调节CMI和疾病结局的关键事件。这里综述的研究表明，细胞内原生动物激活/抑制不同的信号通路和某些巨噬细胞功能是诱导/调节其脊椎动物宿主免疫反应的重要事件，这使得寄生虫和宿主得以存活，从而维持寄生虫的生命周期。
