Suthers Amy N, Sarantopoulos Stefanie
Department of Medicine, Division of Hematological Malignancies and Cellular Therapy, Duke Cancer Institute, Duke University Medical Center, Durham, NC, United States.
Department of Immunology, Duke University Medical Center, Durham, NC, United States.
Front Immunol. 2017 Jul 13;8:775. doi: 10.3389/fimmu.2017.00775. eCollection 2017.
B cells are capable of receptor-mediated responses to foreign antigens. Recognition of microbial-derived nucleic acid (NA) by toll-like receptors (TLRs) 7 and 9 in B cells has been substantiated. Endogenous NA released from damaged or dying cells can also be immunogenic in certain contexts and can incite aberrant activation of B cells. When TLR-driven B cell receptor (BCR)-activated B cells are not properly constrained, pathologic autoantibodies are produced. It is also clear that endosomal TLR7/TLR9 can operate in conjunction with BCR. In addition to BCR signaling, a balance between TLR7 and TLR9 is pivotal in the development of B cell autoreactivity. While TLR9 is important in normal memory B cell responses through BCR, TLR9 activation has been implicated in autoantibody production. Paradoxically, TLR9 also plays known protective roles against autoimmunity by directly and indirectly inhibiting TLR7-mediated autoantibody production. Herein, we summarize literature supporting mechanisms underpinning the promotion of pathological BCR-activated B cells by TLR7 and TLR9. We focus on the literature regarding known points of TLR7/TLR9 and BCR crosstalk. Data also suggest that the degree of TLR responsiveness relies on alterations of certain intrinsic B-cell signaling molecules and is also context specific. Because allogeneic hematopoietic stem cell transplantation is a high NA and B cell-activating factor environment, we conclude that B cell studies of synergistic TLR-BCR signaling in human diseases like chronic graft-versus-host disease are warranted. Further understanding of the distinct molecular pathways mediating TLR-BCR synergy will lead to the development of therapeutic strategies in autoimmune disease states.
B细胞能够对外源抗原产生受体介导的反应。B细胞中Toll样受体(TLR)7和9对微生物来源核酸(NA)的识别已得到证实。受损或死亡细胞释放的内源性NA在某些情况下也具有免疫原性,可引发B细胞的异常激活。当TLR驱动的B细胞受体(BCR)激活的B细胞未得到适当限制时,就会产生病理性自身抗体。同样清楚的是,内体TLR7/TLR9可与BCR协同作用。除了BCR信号传导外,TLR7和TLR9之间的平衡在B细胞自身反应性的发展中至关重要。虽然TLR9在通过BCR的正常记忆B细胞反应中很重要,但TLR9的激活与自身抗体的产生有关。矛盾的是,TLR9还通过直接和间接抑制TLR7介导的自身抗体产生,在自身免疫中发挥已知的保护作用。在此,我们总结了支持TLR7和TLR9促进病理性BCR激活的B细胞机制的文献。我们关注关于TLR7/TLR9与BCR相互作用已知点的文献。数据还表明,TLR反应性的程度依赖于某些内在B细胞信号分子的改变,并且也是上下文特异性的。由于同种异体造血干细胞移植是一个高NA和B细胞激活因子的环境,我们得出结论,有必要对慢性移植物抗宿主病等人类疾病中TLR-BCR协同信号的B细胞进行研究。进一步了解介导TLR-BCR协同作用的不同分子途径将有助于开发自身免疫疾病状态的治疗策略。