Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
FEMS Microbiol Rev. 2012 May;36(3):748-60. doi: 10.1111/j.1574-6976.2011.00318.x. Epub 2011 Dec 22.
The microsporidia are a diverse phylum of obligate intracellular parasites related to the fungi that cause significant and sometimes life-threatening disease in immune-compromised hosts, such as AIDS and organ transplant patients. More recently, their role in causing pathology in immune-competent populations has also been appreciated. Interestingly, in several instances, the microsporidia have been shown to persist in their hosts long term, causing at opposite ends of the spectrum either an intractable chronic diarrhea and wasting in patients with advanced-stage AIDS or asymptomatic shedding of spores in healthy populations. Much remains to be studied regarding the immune response to these pathogens, but it seems clear that CD8+ T cells are essential in clearing infection. However, in the infection models examined thus far, the role for CD4+ T cells is unclear at best. Here, we discuss the possible reasons and ramifications of what may be a weak primary CD4+ T cell response against Encephalitozoon cuniculi. Given the central role of the CD4+ T cell in other models of adaptive immunity, a better appreciation of its role in responding to microsporidia may provide insight into the survival strategies of these pathogens, which allow them to persist in hosts of varied immune status.
微孢子虫是一类与真菌有关的专性细胞内寄生虫，它们在免疫功能低下的宿主中引起严重甚至危及生命的疾病，如艾滋病和器官移植患者。最近，人们也认识到它们在免疫功能正常人群中引起病理学的作用。有趣的是，在某些情况下，微孢子虫在宿主中长期存在，在艾滋病晚期患者中引起难以治愈的慢性腹泻和消瘦，或在健康人群中无症状地排出孢子。关于对这些病原体的免疫反应，仍有许多需要研究，但似乎很清楚，CD8+T 细胞在清除感染中是必不可少的。然而，在迄今为止检查的感染模型中，CD4+T 细胞的作用充其量是不清楚的。在这里，我们讨论了针对兔脑炎微孢子虫可能产生的较弱的初始 CD4+T 细胞反应的原因和后果。鉴于 CD4+T 细胞在其他适应性免疫模型中的核心作用，更好地了解其在应对微孢子虫中的作用可能为这些病原体的生存策略提供深入了解，这些策略使它们能够在免疫状态不同的宿主中存活。
