The innate immune system detects pathogens via germline-encoded receptors that bind to conserved pathogen ligands called pathogen-associated molecular patterns (PAMPs). Here we consider an additional strategy of pathogen sensing called effector-triggered immunity (ETI). ETI involves detection of pathogen-encoded virulence factors, also called effectors. Pathogens produce effectors to manipulate hosts to create a replicative niche and/or block host immunity. Unlike PAMPs, effectors are often diverse and rapidly evolving and can thus be unsuitable targets for direct detection by germline-encoded receptors. Effectors are instead often sensed indirectly via detection of their virulence activities. ETI is a viable strategy for pathogen sensing and is used across diverse phyla, including plants, but the molecular mechanisms of ETI are complex compared to simple receptor/ligand-based PAMP detection. Here we survey the mechanisms and functions of ETI, with a particular focus on emerging insights from animal studies. We suggest that many examples of ETI may remain to be discovered, hiding in plain sight throughout immunology.

中文翻译：

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效应器触发免疫

先天免疫系统通过种系编码受体检测病原体，这些受体与保守的病原体配体（称为病原体相关分子模式（PAMP））结合。在这里，我们考虑另一种病原体感知策略，称为效应触发免疫（ETI）。 ETI 涉及检测病原体编码的毒力因子，也称为效应子。病原体产生效应子来操纵宿主创造复制生态位和/或阻止宿主免疫。与 PAMP 不同，效应器通常具有多样性且快速进化，因此不适合作为种系编码受体直接检测的目标。相反，效应子通常是通过检测其毒力活性来间接感知的。 ETI 是一种可行的病原体传感策略，可用于包括植物在内的多种门，但与简单的基于受体/配体的 PAMP 检测相比，ETI 的分子机制很复杂。在这里，我们调查了 ETI 的机制和功能，特别关注来自动物研究的新见解。我们认为，许多 ETI 的例子可能仍有待发现，在整个免疫学中隐藏在人们的视线中。