Simchoni Noa, Cunningham-Rundles Charlotte
Division of Clinical Immunology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, NY 10029.
Division of Clinical Immunology, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, NY 10029
J Immunol. 2015 Apr 1;194(7):3035-44. doi: 10.4049/jimmunol.1402690. Epub 2015 Mar 4.
B cells activated by nucleic acid-sensing TLR7 and TLR9 proliferate and secrete immune globulins. Memory B cells are presumably more responsive due to higher TLR expression levels, but selectivity and differential outcomes remain largely unknown. In this study, peripheral blood human B cells were stimulated by TLR7 or TLR9 ligands, with or without IFN-α, and compared with activators CD40L plus IL-21, to identify differentially responsive cell populations, defined phenotypically and by BCR characteristics. Whereas all activators induced differentiation and Ab secretion, TLR stimulation expanded IgM(+) memory and plasma cell lineage committed populations, and favored secretion of IgM, unlike CD40L/IL-21, which drove IgM and IgG more evenly. Patterns of proliferation similarly differed, with CD40L/IL-21 inducing proliferation of most memory and naive B cells, in contrast with TLRs that induced robust proliferation in a subset of these cells. On deep sequencing of the IgH locus, TLR-responsive B cells shared patterns of IgHV and IgHJ usage, clustering apart from CD40L/IL-21 and control conditions. TLR activators, but not CD40L/IL-21, similarly promoted increased sharing of CDR3 sequences. TLR-responsive B cells were characterized by more somatic hypermutation, shorter CDR3 segments, and less negative charges. TLR activation also induced long positively charged CDR3 segments, suggestive of autoreactive Abs. Testing this, we found culture supernatants from TLR-stimulated B cells to bind HEp-2 cells, whereas those from CD40L/IL-21-stimulated cells did not. Human B cells possess selective sensitivity to TLR stimulation, with distinctive phenotypic and genetic signatures.
由核酸感应性Toll样受体7（TLR7）和Toll样受体9（TLR9）激活的B细胞会增殖并分泌免疫球蛋白。由于TLR表达水平较高，记忆B细胞可能反应性更强，但选择性和不同的结果在很大程度上仍不清楚。在本研究中，用TLR7或TLR9配体刺激外周血人B细胞，有无干扰素-α（IFN-α）参与，并与激活剂CD40配体（CD40L）加白细胞介素-21（IL-21）进行比较，以识别反应性不同的细胞群体，通过表型和B细胞受体（BCR）特征进行定义。虽然所有激活剂都能诱导分化和抗体分泌，但TLR刺激会扩大IgM(+)记忆细胞和浆细胞系定向群体，并有利于IgM的分泌，这与CD40L/IL-21不同，后者能更均匀地驱动IgM和IgG的分泌。增殖模式也同样不同，CD40L/IL-21能诱导大多数记忆B细胞和幼稚B细胞增殖，而TLR则能在这些细胞的一个亚群中诱导强烈增殖。对免疫球蛋白重链（IgH）基因座进行深度测序时，TLR反应性B细胞具有共享的IgHV和IgHJ使用模式，与CD40L/IL-21及对照条件聚类不同。同样，TLR激活剂而非CD40L/IL-21能促进互补决定区3（CDR3）序列共享增加。TLR反应性B细胞的特征是更多的体细胞超突变、更短的CDR3片段和更少的负电荷。TLR激活还能诱导长的带正电荷的CDR3片段，提示自身反应性抗体。对此进行测试时，我们发现来自TLR刺激的B细胞的培养上清液能结合人喉癌上皮细胞（HEp-2细胞），而来自CD40L/IL-21刺激细胞的上清液则不能。人B细胞对TLR刺激具有选择性敏感性，具有独特的表型和遗传特征。
