Vaccine adjuvants containing analogs of microbial products activate pattern recognition receptors (PRRs) on antigen-presenting cells, including monocytes and macrophages, which can cause prostaglandin E₂ (PGE₂) release and consequently undesired inflammatory responses and fever in vaccine recipients. Here, we studied the mechanism of PGE₂ production by human monocytes activated with muramyl dipeptide (MDP) adjuvant, which activates cytosolic nucleotide-binding oligomerization domain 2 (NOD2). In rabbits, administration of MDP elicited an early increase in PGE₂ followed by fever. In human monocytes, MDP alone did not induce PGE₂ production. However, high amounts of PGE₂ and the proinflammatory cytokines IL-1β and IL-6 were secreted by monocytes activated with MDP in the presence of conditioned medium obtained from CD3 bead–isolated T cells (Tc CM) but not from those isolated without CD3 beads. Mass spectrometry and immunoblotting revealed that the costimulatory factor in Tc CM was glycoprotein Ib α (GPIbα). Antibody-mediated blockade of GPIbα or of its receptor, Mac-1 integrin, inhibited the secretion of PGE₂, IL-1β, and IL-6 in MDP + Tc CM–activated monocytes, whereas recombinant GPIbα protein increased PGE₂ production by MDP-treated monocytes. In vivo, COX2 mRNA abundance was reduced in the liver and spleen of Mac-1 KO mice after administration of MDP compared with that of treated wild-type mice. Our findings suggest that the production of PGE₂ and proinflammatory cytokines by MDP-activated monocytes is mediated by cooperation between two signaling pathways: one delivered by MDP through NOD2 and a second through activation of Mac-1 by T cell–derived GPIbα.

含有微生物产物类似物的疫苗佐剂会激活抗原呈递细胞（包括单核细胞和巨噬细胞）上的模式识别受体（PRR），这会导致前列腺素E ₂（PGE ₂）释放，从而导致疫苗接种者产生不良的炎症反应和发烧。在这里，我们研究了人类的单双核细胞被鼠李二肽（MDP）佐剂激活后产生PGE ₂的机制，该佐剂可以激活胞质核苷酸结合寡聚域2（NOD2）。在家兔中，MDP的使用引起PGE ₂的早期升高，然后发烧。在人单核细胞中，单独的MDP不会诱导PGE _2的产生。但是，大量的PGE ₂在从CD3珠分离的T细胞（Tc CM）获得的条件培养基存在下，由MDP激活的单核细胞分泌促炎细胞因子IL-1β和IL-6，但从没有CD3珠分离的条件培养基中不分泌促炎细胞因子IL-1β和IL-6。质谱和免疫印迹表明，Tc CM中的共刺激因子是糖蛋白Ibα（GPIbα）。抗体介导的GPIbα或其受体Mac-1整合素的阻滞抑制了MDP + Tc CM激活的单核细胞中PGE ₂，IL-1β和IL-6的分泌，而重组GPIbα蛋白增加了MDP产生PGE _2的能力。处理的单核细胞。体内，COX2与治疗后的野生型小鼠相比，施用MDP后Mac-1 KO小鼠的肝脏和脾脏中的mRNA丰度降低。我们的发现表明，由MDP激活的单核细胞产生PGE ₂和促炎性细胞因子是由两种信号途径之间的协作介导的：一种是MDP通过NOD2传递的，另一种是通过T细胞衍生的GPIbα激活Mac-1的。