来自澳大利亚国立大学，英国癌症研究中心等处的研究人员发表了题为“Identification of Bcl-6-dependent follicular helper NKT cells that provide cognate help for B cell responses”的文章，发现了一种新型的免疫系统辅助细胞：滤泡辅助性自然杀伤T细胞（NKTFH），这将有助于科学家们深入了解人体抵抗感染和知名疾病的机理。相关成果公布在Nature Immunology，以及Immunity杂志上。
自然杀伤T细胞（NKT cells）是机体重要的免疫细胞，具有NK和T细胞的标志，在抗击感染和其它免疫过程中起了重要作用，如过敏、癌症和自身免疫性疾病。这类细胞与仅仅通过蛋白识别细菌的其它T细胞不同，它是通过脂质来识别细菌。它们可以引起致命的感染，包括脑膜炎和肺炎，自然杀伤T细胞不仅仅识别脂质，而且还可以被这些脂质激活。
在这篇文章中，研究人员发现了一种新型细胞NKTFH，这种细胞可以识别出侵入人体细菌上的脂质抗原，脂质抗原一旦被识别，NKTFH细胞就会让B细胞产生抗体反应，这将有助于人体提升对抗感染和疾病的能力。
研究人员认为NKTFH细胞是自然杀伤T细胞的亚型，专门负责让识别含脂质抗原的B细胞产生抗体反应。NKTFH细胞还会诱导称为发生中心的特殊结构，与对蛋白抗原产生高亲和抗体反应的情况类似。这些特性都会提高B细胞的能力，从而增强人体的免疫系统和抗感染能力。而且研究人员还发现，NKTFH细胞提高B细胞能力的时间是短暂的，不会让B细胞长时间产生抗体。
NKTFH细胞是通过一种天然的、非化学的方式在使用抗体与病菌对抗之前就识别如肺炎和脑膜炎的感染细菌。这一发现将帮助研究人员加深对人体复杂免疫系统的了解。而且通过了解抗体是如何产生来保护我们免受细菌侵袭，有助于疫苗的发展，同时能帮助更好地了解免疫反应。
研究人员还提出，以往科学家们一直认为T细胞和自然杀手T滤泡性辅助细胞属同类，但现在他们才知道其实这些细胞不仅是一个类型，而且每种细胞在免疫系统中都拥有其非常独特的作用。
原文摘要：
Identification of Bcl-6-dependent follicular helper NKT cells that provide cognate help for B cell responses
Lipid antigens trigger help from natural killer T cells (NKT cells) for B cells, and direct conjugation of lipid agonists to antigen profoundly augments antibody responses. Here we show that in vivo, NKT cells engaged in stable and prolonged cognate interactions with B cells and induced the formation of early germinal centers. Mouse and human NKT cells formed CXCR5+PD-1hi follicular helper NKT cells (NKTFH cells), and this process required expression of the transcriptional repressor Bcl-6, signaling via the coreceptor CD28 and interaction with B cells. NKTFH cells provided direct cognate help to antigen-specific B cells that was dependent on interleukin 21 (IL-21). Unlike T cell–dependent germinal centers, those driven by NKTFH cells did not generate long-lived plasma cells. Our results demonstrate the existence of a Bcl-6-dependent subset of NKT cells specialized in providing help to B cells.
How T cells earn the follicular rite of passage
The discovery that Bcl-6 was the transcriptional regulator of follicular helper T (Tfh) cells completed the recognition of this population as an effector subset specialized in the provision of help to B cells. Improved reagents and recent models that allow tracking of Bcl-6-expressing T cells have revealed that the decision to become a Tfh cell occurs soon after T cells are primed by dendritic cells and start dividing, before interaction with B cells. The latter are important for sustaining Bcl-6 expression. Bcl-6 coordinates a signaling program that changes expression or function of multiple guidance receptors, leading to Tfh cell localization within germinal centers. This program is not unique to CD4(+) helper T cells; FoxP3(+) regulatory T cells and NKT cells co-opt the follicular differentiation pathway to enter the follicle and become specialized follicular cells. This review will focus on recent insights into the early events that determine Tfh cell differentiation.
（责任编辑：labweb）
