In order to get recognized by CD8 T cells, most cells present peptides from endogenously expressed self or foreign proteins on MHC class I molecules. However, specialized antigen-presenting cells, such as DCs and macrophages, can present exogenous antigen on MHC-I in a process called cross-presentation. This pathway plays key roles in antimicrobial and antitumor immunity, and also immune tolerance. Recent advances have broadened our understanding of the underlying mechanisms of cross-presentation. Here, we review some of these recent advances, including the distinct pathways that result in the cross-priming of CD8 T cells and the source of the class I molecules presenting exogenous peptides.

中文翻译：

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MHC I分子上外源抗原的交叉呈递。

为了被 CD8 T 细胞识别，大多数细胞在 MHC I 类分子上呈递来自内源性表达的自身或外源蛋白的肽。然而，特化的抗原呈递细胞，如 DCs 和巨噬细胞，可以在称为交叉呈递的过程中在 MHC-I 上呈递外源抗原。该途径在抗菌和抗肿瘤免疫以及免疫耐受中起关键作用。最近的进展拓宽了我们对交叉呈现的潜在机制的理解。在这里，我们回顾了其中一些最近的进展，包括导致 CD8 T 细胞交叉启动的不同途径和呈递外源肽的 I 类分子的来源。