Marcoux Genevieve, Laroche Audrée, Hasse Stephan, Bellio Marie, Mbarik Maroua, Tamagne Marie, Allaeys Isabelle, Zufferey Anne, Lévesque Tania, Rebetz Johan, Karakeussian-Rimbaud Annie, Turgeon Julie, Bourgoin Sylvain G, Hamzeh-Cognasse Hind, Cognasse Fabrice, Kapur Rick, Semple John W, Hébert Marie-Josée, Pirenne France, Overkleeft Herman S, Florea Bogdan I, Dieude Mélanie, Vingert Benoît, Boilard Eric
Centre de Recherche, Centre Hospitalier Universitaire de Québec-Université Laval, Québec, QC, Canada.
Centre de Recherche Arthrite, Faculté de Médecine de l'Université Laval, Québec, QC, Canada.
Blood. 2021 Dec 23;138(25):2607-2620. doi: 10.1182/blood.2020009957.
In addition to their hemostatic role, platelets play a significant role in immunity. Once activated, platelets release extracellular vesicles (EVs) formed by the budding of their cytoplasmic membranes. Because of their heterogeneity, platelet EVs (PEVs) are thought to perform diverse functions. It is unknown, however, whether the proteasome is transferred from platelets to PEVs or whether its function is retained. We hypothesized that functional protein processing and antigen presentation machinery are transferred to PEVs by activated platelets. Using molecular and functional assays, we found that the active 20S proteasome was enriched in PEVs, along with major histocompatibility complex class I (MHC-I) and lymphocyte costimulatory molecules (CD40L and OX40L). Proteasome-containing PEVs were identified in healthy donor blood, but did not increase in platelet concentrates that caused adverse transfusion reactions. They were augmented, however, after immune complex injections in mice. The complete biodistribution of murine PEVs after injection into mice revealed that they principally reached lymphoid organs, such as spleen and lymph nodes, in addition to the bone marrow, and to a lesser extent, liver and lungs. The PEV proteasome processed exogenous ovalbumin (OVA) and loaded its antigenic peptide onto MHC-I molecules, which promoted OVA-specific CD8+ T-lymphocyte proliferation. These results suggest that PEVs contribute to adaptive immunity through cross-presentation of antigens and have privileged access to immune cells through the lymphatic system, a tissue location that is inaccessible to platelets.
除了其止血作用外，血小板在免疫中也发挥着重要作用。一旦被激活，血小板就会释放由其细胞质膜出芽形成的细胞外囊泡（EVs）。由于其异质性，血小板衍生的细胞外囊泡（PEVs）被认为具有多种功能。然而，蛋白酶体是否从血小板转移到PEVs，或者其功能是否得以保留尚不清楚。我们推测，功能性蛋白质加工和抗原呈递机制会被激活的血小板转移到PEVs。通过分子和功能分析，我们发现活性20S蛋白酶体在PEVs中富集，同时还有主要组织相容性复合体I类（MHC-I）和淋巴细胞共刺激分子（CD40L和OX40L）。在健康供体血液中发现了含有蛋白酶体的PEVs，但在引起不良输血反应的血小板浓缩物中并未增加。然而，在给小鼠注射免疫复合物后，它们的数量增加了。将小鼠PEVs注射到小鼠体内后的完整生物分布显示，除了骨髓外，它们主要到达脾脏和淋巴结等淋巴器官，在较小程度上还到达肝脏和肺。PEV蛋白酶体对外源卵清蛋白（OVA）进行加工，并将其抗原肽加载到MHC-I分子上，从而促进OVA特异性CD8+T淋巴细胞增殖。这些结果表明，PEVs通过抗原交叉呈递促进适应性免疫，并通过淋巴系统优先接触免疫细胞，而血小板无法进入该组织部位。
