CD4+ T cells are the central element of the adaptive immune responses and protect the body from a variety of pathogens. Starting from naive cells, CD4+ T cells can differentiate into various effector cell subsets with specialized functions including T helper (Th) 1, Th2, Th17, regulatory T (Treg) and T follicular helper (Tfh) cells. Among them, Tregs and Th17 cells show a strong plasticity allowing the functional adaptation to various physiological and pathological environments during immune responses. Although they are derived from the same precursor cells and their differentiation pathways are interrelated, the terminally differentiated cells have totally opposite functions. Studies have shown that Tregs and Th17 cells have rather complex interplays in viral infection: Th17 cells may contribute to immune activation and disease progression while Tregs may inhibit this process and play a key role in the maintenance of immune homoeostasis, possibly at the cost of compromised viral control. In this review, we take respiratory syncytial virus (RSV), hepatitis B virus (HBV)/hepatitis C virus (HCV) and human immunodeficiency virus (HIV) infections as examples to discuss these interplays and their impacts on disease progression in viral infection.

中文翻译：

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病毒感染中的调节性T细胞和T辅助17细胞。

CD4 + T细胞是适应性免疫反应的核心要素，可保护人体免受多种病原体的侵害。从幼稚细胞开始，CD4 + T细胞可以分化成具有特殊功能的各种效应细胞亚群，包括T辅助细胞（Th），Th2，Th17，调节性T（Treg）和T滤泡辅助细胞（Tfh）。其中，Tregs和Th17细胞显示出强大的可塑性，在免疫反应过程中可以适应各种生理和病理环境。尽管它们源自相同的前体细胞，并且它们的分化途径是相互关联的，但最终分化的细胞却具有完全相反的功能。研究表明，Tregs和Th17细胞在病毒感染中具有相当复杂的相互作用：Th17细胞可能有助于免疫激活和疾病进展，而Tregs可能抑制该过程并在维持免疫同调中起关键作用，可能以损害病毒控制为代价。在本文中，我们以呼吸道合胞病毒（RSV），乙型肝炎病毒（HBV）/丙型肝炎病毒（HCV）和人免疫缺陷病毒（HIV）感染为例，讨论了这些相互作用及其对病毒感染疾病进展的影响。