Gastroenterology：肠上皮释放外泌体(exosome)加强抗原呈递 - 外泌体之家 | 细胞外膜泡领域核心平台—exosomes & microvesicles—小膜泡大作用

背景和目的：体内研究发现，在主要组织相容性复合体II/肽复合体的作用下，肠上皮细胞释放抗原提呈囊泡（外泌体），刺激特异性免疫应答反应。为了进一步研究人上皮细胞外泌体在抗原提呈中的作用，本文通过体外实验分析了外泌体负载抗原肽、结合免疫靶细胞及诱导T细胞活化的能力。

方法：在人单核细胞来源的树突状细胞存在或缺失情况下，研究T84肠上皮细胞HLA-DR4表达株来源的外泌体负载HLA-DR4特异性肽3H-HAS 64-76及激活HLA-DR4限制性T细胞杂交细胞的能力。采用流式细胞术和共聚焦显微镜分析异硫氰酸荧光素标记的外泌体与T细胞及DCs细胞之间的相互作用。

结果：T84细胞外泌体富含CD9，CD81，CD82和A33抗原，能够特异性结合人血清白蛋白64-76多肽的HLA-DR4分子，并更易与DCs细胞相互作用。HSA负载的外泌体不能直接激活T细胞杂交细胞，但是能通过DCs诱导T细胞活化。当HAS多肽结合到外泌体HLA-DR4分子上，而不是以可溶性形式存在时，DCs细胞多肽提呈的阈值显著降低（×10-3）。

结论：在外源性多肽及主要组织相容性复合体II的作用下，肠上皮细胞释放外泌体，并更易与DCs发生相互作用，显著增强多肽向T细胞提呈能力。上皮细胞外泌体通过介导少量管腔抗原信息的传递，在粘膜表面发挥免疫监视作用，从而将细胞抗原和局部免疫细胞之间紧密关联。

Background & Aims: Intestinal epithelial cells release antigen-presenting vesicle (exosomes) bearing major histocompatibility complex class II/peptide complexes stimulating specific immune responses in vivo. To characterize further the role of human epithelial exosomes in antigen presentation, their capacity to load antigenic peptides, bind immune target cells, and induce T-cell activation was analyzed in vitro. Methods: The capacity of exosomes derived from the HLA-DR4-expressing, intestinal epithelial cell line T84 to load the HLA-DR4-specific peptide3H-HSA 64–76 and to activate a HLA-DR4-restricted T-cell hybridoma was tested in the presence or absence of human monocyte-derived dendritic cells（DCs）. Interaction of fluorescein isothiocyanate-labeled exosomes with T cells and DCs was analyzed by flow cytometry and confocal microscopy.

Results: T84-derived exosomes, enriched in CD9, CD81, CD82,and A33 antigen, were capable of binding specifically human serum albumin （HSA） 64–76 peptide on HLADR4 molecules and of interacting preferentially with DCs. HSA-loaded exosomes were unable to activate the T-cell hybridoma directly but induced a productive T-cell activation through DCs. When HSA peptide was bound to exosomal HLA-DR4 molecules instead of in a soluble form, the threshold of peptide presentation by DCs was markedly decreased (×10-3).

Conclusions: Exosomes released by intestinal epithelial cells bear exogenous peptides complexed to major histocompatibility complex class II molecules and interact preferentially with DCs, strongly potentiating peptide presentation to T cells. Epithelial exosomes constitute a powerful link between luminal antigens and local immune cells by mediating the transfer of tiny amounts of luminal antigenic information and facilitating immune surveillance at mucosal surfaces.

外泌体之家 | 细胞外膜泡领域核心平台—exosomes &amp; microvesicles—小膜泡大作用

外泌体之家 | 细胞外膜泡领域核心平台—exosomes & microvesicles—小膜泡大作用