In addition to the expression of antigen on its surface, activated t cell releases various kinds of active substances, including cytokines, to regulate series of immunological responses.

细胞活化后除了表达细胞表面活化抗原外，主要释放多种活性物质发挥免疫调节功能，细胞因子是其中重要的一种。

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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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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