B cells have been known for their ability to present antigens to T cells for almost 40 years. However, the precise roles of B cell antigen presentation in various immune responses are not completely understood. The term “professional” antigen‐presenting cells (APCs) was proposed to distinguish APCs that are required for initiating the immune responses from those use antigen presentation to enhance their own effector functions. Unlike dendritic cells, which are defined as professional APCs for their well‐established functions in activating naive T cells, B cells have been shown in the past to mostly present antigens to activated CD4+ T cells mainly to seek help from T helper cells. However, recent evidence suggested that B cells can act as professional APCs under infectious conditions or conditions mimicking viral infections. B cell antigen receptors (BCRs) and the innate receptor Toll‐like receptors are activated synergistically in response to pathogens or virus‐like particles, under which conditions B cells are not only potent but also the predominant APCs to turn naive CD4+ T cells into T follicular helper cells. The discovery of B cells as professional APCs to initiate CD4+ T cell response provides a new insight for both autoimmune diseases and vaccine development.

中文翻译：

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B 细胞抗原呈递在 CD4+ T 细胞反应启动中的作用。

近 40 年来，B 细胞以其向 T 细胞呈递抗原的能力而闻名。然而，B 细胞抗原呈递在各种免疫反应中的确切作用尚不完全清楚。提出了“专业”抗原呈递细胞 (APC) 一词，以将启动免疫反应所需的 APC 与使用抗原呈递以增强其自身效应子功能的 APC 区分开来。与树突状细胞不同，树突状细胞因其在激活幼稚 T 细胞方面的成熟功能而被定义为专业 APC，而 B 细胞在过去已被证明主要将抗原呈递给激活的 CD4+ T 细胞，主要是为了寻求 T 辅助细胞的帮助。然而，最近的证据表明，B 细胞可以在感染条件或模拟病毒感染的条件下充当专业 APC。B 细胞抗原受体 (BCR) 和先天性受体 Toll 样受体协同激活以响应病原体或病毒样颗粒，在这种情况下，B 细胞不仅有效，而且还是将幼稚 CD4+ T 细胞转变为 T 细胞的主要 APC滤泡辅助细胞。B 细胞作为启动 CD4+ T 细胞反应的专业 APC 的发现为自身免疫性疾病和疫苗开发提供了新的见解。