Zellbiologie, Deutsches Rheuma-Forschungszentrum, ein Institut der Leibniz-Gemeinschaft, 10117 Berlin, Germany;
Berlin-Brandenburg School for Regenerative Therapies, Charité Universitätsmedizin Berlin, 13353 Berlin, Germany.
J Immunol. 2018 Jun 15;200(12):3981-3992. doi: 10.4049/jimmunol.1701728. Epub 2018 May 7.
There are currently limited insights into the progression of human primary humoral immunity despite numerous studies in experimental models. In this study, we analyzed a primary and related secondary parenteral keyhole limpet hemocyanin (KLH) immunization in five human adults. The primary challenge elicited discordant KLH-specific serum and blood effector B cell responses (i.e., dominant serum KLH-specific IgG and IgM levels versus dominant KLH-specific IgA plasmablast frequencies). Single-cell IgH sequencing revealed early appearance of highly (>15 mutations) mutated circulating KLH-specific plasmablasts 2 wk after primary KLH immunization, with simultaneous KLH-specific plasmablasts carrying non- and low-mutated IgH sequences. The data suggest that the highly mutated cells might originate from cross-reactive memory B cells (mBCs) rather than from the naive B cell repertoire, consistent with previous reported mutation rates and the presence of KLH-reactive mBCs in naive vaccinees prior to immunization. Whereas upon secondary immunization, serum Ab response kinetics and plasmablast mutation loads suggested the exclusive reactivation of KLH-specific mBCs, we, however, detected only little clonal overlap between the peripheral KLH-specific secondary plasmablast IgH repertoire and the primary plasmablast and mBC repertoire, respectively. Our data provide novel mechanistic insights into human humoral immune responses and suggest that primary KLH immunization recruits both naive B cells and cross-reactive mBCs, whereas secondary challenge exclusively recruits from a memory repertoire, with little clonal overlap with the primary response.
尽管在实验模型中进行了大量研究，但目前对人类初级体液免疫的进展仍知之甚少。在这项研究中，我们分析了五名成年人中初次和相关的二次静脉注射血蓝蛋白（KLH）免疫。初次挑战引起了不一致的 KLH 特异性血清和血液效应 B 细胞反应（即，占主导地位的血清 KLH 特异性 IgG 和 IgM 水平与占主导地位的 KLH 特异性 IgA 浆母细胞频率）。单细胞 IgH 测序显示，在初次 KLH 免疫后 2 周，早期出现了高度（>15 个突变）突变的循环 KLH 特异性浆母细胞，同时携带非突变和低突变 IgH 序列的 KLH 特异性浆母细胞。这些数据表明，高度突变的细胞可能来自交叉反应性记忆 B 细胞（mBC），而不是来自幼稚 B 细胞库，与先前报道的突变率以及在免疫前幼稚疫苗接种者中存在 KLH 反应性 mBC 一致。虽然在二次免疫中，血清 Ab 反应动力学和浆母细胞突变负荷表明 KLH 特异性 mBC 的特异性再激活，但我们仅检测到外周 KLH 特异性二次浆母细胞 IgH 库与原发性浆母细胞和 mBC 库之间的克隆重叠很少。我们的数据为人类体液免疫反应提供了新的机制见解，并表明初次 KLH 免疫既招募了幼稚 B 细胞，又招募了交叉反应性 mBC，而二次挑战仅从记忆库中招募，与初次反应的克隆重叠很少。
