Cross-presentation is increasingly recognized as a key mechanism by which specific antigen-presenting cells (APCs) activate the cellular immune system against virally infected or neoplastic cells. These APCs have the capacity to acquire exogenous proteins by phagocytosis or endocytosis, derive antigenic peptides, and then cross-present them in the context of class I major histocompatibility complex molecules. Because APCs provide both an antigenic stimulus and costimulatory signals, they can effectively activate naive CD8+ T lymphocytes, resulting in a brisk cellular immune response. The precise cellular pathways that permit an exogenous antigen to be presented in the context of class I major histocompatibility complex is the focus of intense investigation that has illuminated our understanding of the cell biology of APCs. This article reviews our understanding of how APCs cross-present antigen, illustrating how this process differs from the canonical pathways of antigen presentation. We define the central players required for cross-presentation and then focus on recent studies that reveal the molecular mechanisms underlying this phenomenon. Understanding these mechanisms will likely inform the development of effective cell-based vaccines and other cellular immunotherapies and is therefore of interest to practitioners of transfusion medicine.

中文翻译：

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对抗原向免疫系统交叉呈递的分子解释。

交叉呈递越来越被认为是一种关键机制，特定抗原呈递细胞（APC）通过这种机制激活针对病毒感染或赘生性细胞的细胞免疫系统。这些APC具有通过吞噬作用或内吞作用获取外源蛋白质，衍生抗原肽，然后在I类主要组织相容性复合物分子中交叉呈递的能力。因为APC同时提供抗原刺激和共刺激信号，所以它们可以有效激活天然CD8 + T淋巴细胞，从而引起轻快的细胞免疫反应。允许在I类主要组织相容性复合物的背景下呈递外源抗原的精确细胞途径是深入研究的重点，这阐明了我们对APC细胞生物学的理解。本文回顾了我们对APC如何交叉呈递抗原的理解，说明了该过程与抗原呈递的典型途径有何不同。我们定义了交叉演示所需的核心参与者，然后重点关注揭示此现象潜在分子机制的最新研究。了解这些机制很可能会为有效的基于细胞的疫苗和其他细胞免疫疗法的发展提供信息，因此对于输血医学从业者来说很有意义。