Schettino E W, Chai S K, Kasaian M T, Schroeder H W, Casali P
Department of Pathology, Cornell University Medical College, New York 10021, USA.
J Immunol. 1997 Mar 1;158(5):2477-89.
To understand whether the distinct VHDJH gene utilization by natural polyreactive Abs reflects the developmentally restricted Ig VHDJH rearrangements putatively expressed by B-1 cells, we generated 11 (8 IgM, 1 IgG3, 2 IgA1), 7 (6 IgM, 1 IgG1), and 7 (2 IgM, 3 IgG1, 2 IgG3) mAb-producing lines using B-1a (surface CD5+, CD45RAlow), B-1b (surface CD5-, CD45RAlow, CD5 mRNA+), and B-2 (surface CD5-, CD45RAhigh, CD5 mRNA-) cells, respectively, sorted from adult human peripheral blood. Most B-1a and B-1b, but no B-2, cell-derived mAbs were polyreactive; i.e., they bound different self and foreign Ags with different affinities. B-1a and B-2 mAbs preferentially utilized VH4 (p = 0.003) and VH3 (p = 0.010) genes, respectively. All three mAb populations utilized DXP, DLR, DN DH genes, and JH6, but no mAb utilized DHQ52. There were fewer unencoded nucleotide (N) additions in the VHDJH junctions of B-1b (3.00 +/- 2.52, mean +/- SD) than of B-1a (12.45 +/- 3.93, p = 1.23 x 10(-5)) or B-2 (8.29 +/- 4.75, p = 0.020) mAbs. Partly due to the fewer N additions and a paucity of D-D fusions, the B-1b mAb CDR3s were significantly shorter than the B-1a mAb CDR3s (p = 0.013), which contained a nonrandom Tyr distribution (p = 0.003). Finally, all but two B-1 cell-derived mAbs were mutated, in a fashion similar to that of the Ag-selected B-2 mAbs. Thus, in the human adult, B-1 cells that make natural polyreactive Abs may not be representative of the predominantly B-1 developmental waves of colonization of the fetal and neonatal B cell repertoires, and are somatically selected.
为了了解天然多反应性抗体对不同VHDJH基因的利用是否反映了B-1细胞假定表达的发育受限的Ig VHDJH重排，我们分别使用从成人外周血中分离出的B-1a（表面CD5+、CD45RAlow）、B-1b（表面CD5-、CD45RAlow、CD5 mRNA+）和B-2（表面CD5-、CD45RAhigh、CD5 mRNA-）细胞，生成了11个（8个IgM、1个IgG3、2个IgA1）、7个（6个IgM、1个IgG1）和7个（2个IgM、3个IgG1、2个IgG3）产生单克隆抗体的细胞系。大多数源自B-1a和B-1b细胞的单克隆抗体具有多反应性，而源自B-2细胞的单克隆抗体则没有；也就是说，它们以不同亲和力结合不同的自身和外来抗原。B-1a和B-2单克隆抗体分别优先利用VH4基因（p = 0.003）和VH3基因（p = 0.010）。所有三个单克隆抗体群体都利用DXP、DLR、DN DH基因和JH6，但没有单克隆抗体利用DHQ52。B-1b单克隆抗体VHDJH连接区未编码核苷酸（N）的添加数（3.00 +/- 2.52，平均值 +/- 标准差）少于B-1a单克隆抗体（12.45 +/- 3.93，p = 1.23 x 10-5）或B-2单克隆抗体（8.29 +/- 4.75，p = 0.020）。部分由于N添加数较少以及D-D融合缺乏，B-1b单克隆抗体的互补决定区3（CDR3）明显短于B-1a单克隆抗体的CDR3（p = 0.013），B-1a单克隆抗体的CDR3含有非随机的酪氨酸分布（p = 0.003）。最后，除了两个源自B-1细胞的单克隆抗体外，所有单克隆抗体都发生了突变，其方式类似于抗原选择的B-2单克隆抗体。因此，在成年人体内，产生天然多反应性抗体的B-1细胞可能不代表胎儿和新生儿B细胞库中主要的B-1发育波，并且是经过体细胞选择的。
