Department of Immunology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan.
Research and Development Department, Japan BCG Laboratory, Tokyo, Japan.
Nat Commun. 2021 Apr 16;12(1):2299. doi: 10.1038/s41467-021-22620-3.
Mycobacterial cell-wall glycolipids elicit an anti-mycobacterial immune response via FcRγ-associated C-type lectin receptors, including Mincle, and caspase-recruitment domain family member 9 (CARD9). Additionally, mycobacteria harbor immuno-evasive cell-wall lipids associated with virulence and latency; however, a mechanism of action is unclear. Here, we show that the DAP12-associated triggering receptor expressed on myeloid cells 2 (TREM2) recognizes mycobacterial cell-wall mycolic acid (MA)-containing lipids and suggest a mechanism by which mycobacteria control host immunity via TREM2. Macrophages respond to glycosylated MA-containing lipids in a Mincle/FcRγ/CARD9-dependent manner to produce inflammatory cytokines and recruit inducible nitric oxide synthase (iNOS)-positive mycobactericidal macrophages. Conversely, macrophages respond to non-glycosylated MAs in a TREM2/DAP12-dependent but CARD9-independent manner to recruit iNOS-negative mycobacterium-permissive macrophages. Furthermore, TREM2 deletion enhances Mincle-induced macrophage activation in vitro and inflammation in vivo and accelerates the elimination of mycobacterial infection, suggesting that TREM2-DAP12 signaling counteracts Mincle-FcRγ-CARD9-mediated anti-mycobacterial immunity. Mycobacteria, therefore, harness TREM2 for immune evasion.
分枝杆菌细胞壁糖脂通过 FcRγ 相关 C 型凝集素受体(包括 Mincle 和 caspase 募集结构域家族成员 9(CARD9))引发抗分枝杆菌免疫反应。此外,分枝杆菌还具有与毒力和潜伏相关的免疫逃避细胞壁脂质;然而,其作用机制尚不清楚。在这里,我们表明,髓样细胞表达的 DAP12 相关触发受体 2(TREM2)识别分枝杆菌细胞壁含有酰基的分枝菌酸(MA)的脂质,并提出了一种分枝杆菌通过 TREM2 控制宿主免疫的机制。巨噬细胞以依赖于 Mincle/FcRγ/CARD9 的方式对糖基化 MA 脂质作出反应,以产生炎症细胞因子并招募诱导型一氧化氮合酶(iNOS)阳性的杀分枝杆菌巨噬细胞。相反,巨噬细胞以依赖于 TREM2/DAP12 但不依赖于 CARD9 的方式对非糖基化的 MA 作出反应,以招募 iNOS 阴性的分枝杆菌允许的巨噬细胞。此外,TREM2 缺失增强了体外 Mincle 诱导的巨噬细胞活化和体内炎症,并加速了分枝杆菌感染的消除,这表明 TREM2-DAP12 信号传导拮抗了 Mincle-FcRγ-CARD9 介导的抗分枝杆菌免疫。因此,分枝杆菌利用 TREM2 进行免疫逃避。
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