Before a helper t cell can trigger a response to a pathogen or parasite, it has to "feel" these molecular bits of an invader displayed on the surface of an antigen-presenting cell (APC).

在辅助T细胞激发针对病原的免疫反应之前，它必须感觉到位于抗原递呈细胞面表的入侵者分子片段。

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T cell can only recognize specific antigenic peptide-MHC complex on antigen-presenting cell. This is MHC restriction in antigen recognition of t cell.

细胞只能识别抗原提呈细胞表面特定的抗原肽MHC分子复合物，这就是T细胞抗原识别的MHC限制。

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But this antigen presenting cell is more likely a professional antigen presenting cell, or a subset of cells of your immune system that are specialized in ingesting foreign particles and displaying their contents to the rest of the immune system.

但这种抗原呈递细胞更加类似于,专职抗原呈递细胞,或者是体内免疫细胞中的一个亚群,专门从事吞噬异己物质,并告知免疫系统的其他细胞的工作

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Now, for antibody production it is still a T-cell that recognizes the antigen presenting cell.

现在,抗体的产生,仍是源于T淋巴细胞识别出抗原呈递细胞

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For a T cell to become active, it must receive signals from another part of the immune system called an antigen-presenting cell.

ECONOMIST: Breaching the body's defences

However, before the alarm can be sounded in this way, proteins on the surface of the antigen-presenting cell and the T cell must bind together in what is called a cellular handshake.

ECONOMIST: Breaching the body's defences