PD-1 as an immune checkpoint molecule down-regulates T cell activity during immune responses in order to prevent autoimmune tissue damage. In chronic infections or tumors, lasting antigen-exposure leads to permanent PD-1 expression that can limit immune-mediated clearance of pathogens or degenerated cells. Blocking PD-1 can enhance T cell function; in cancer treatment PD-1 blockade is already used as a successful therapy. However, the role of PD-1 expression and blocking in the context of acute and chronic infections is less defined. Building on its success in cancer therapy leads to the hypothesis that blocking PD-1 in infectious diseases is also beneficial in acute or chronic infections. This review will focus on the role of PD-1 expression in acute and chronic infections with virus, bacteria, and parasites, with a particular focus on recent studies regarding PD-1 blockade in infectious diseases.

中文翻译：

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PD-1在急性和慢性感染中的作用。

PD-1作为免疫检查点分子，在免疫应答过程中下调T细胞活性，以防止自身免疫组织损伤。在慢性感染或肿瘤中，持久的抗原暴露会导致永久性PD-1表达，从而限制免疫介导的病原体或变性细胞清除。阻断PD-1可增强T细胞功能；在癌症治疗中，PD-1封锁已被用作成功的疗法。但是，PD-1表达和阻断在急性和慢性感染中的作用尚不清楚。基于其在癌症治疗中的成功经验，得出这样的假设：在传染病中阻断PD-1对急性或慢性感染也有益处。这篇评论的重点是PD-1表达在病毒和细菌以及寄生虫的急性和慢性感染中的作用，