Harindranath N, Ikematsu H, Notkins A L, Casali P
Laboratory of Oral Medicine, National Institute of Dental Research, National Institutes of Health, Bethesda, MD 20892.
Int Immunol. 1993 Dec;5(12):1523-33. doi: 10.1093/intimm/5.12.1523.
B lymphocytes committed to the production of antibodies binding to antigens on pathogenic bacteria and viruses (natural antibodies) are common components of the normal human B cell repertoire. A major proportion of natural antibodies is capable of binding multiple antigens (polyreactive antibodies). Using B cells from three HIV-1 seronegative healthy subjects, and purified HIV-1 and beta-galactosidase from Escherichia coli as selecting antigen, we generated three natural IgM mAb to HIV-1 and a natural IgM mAb to beta-galactosidase. The three HIV-1-selected antibodies (mAb102, mAb103, and mAb104) were polyreactive. They bound with different affinities (Kd = 10(-6) to 10(-8) M) to the HIV-1 envelope gp160, the p24 core protein, and the p66 reverse transcriptase, but not to the 120 glycosylated env protein. They also bound to beta-galactosidase (Kd approximately 10(-7) M), tetanus toxoid, and various various self antigens. In contrast, the natural mAb selected for binding to beta-galactosidase (mAb207.F1) was monoreactive, in that it bound with a high affinity (Kd < 10(-8) M) to this antigen, but to none of the other antigens tested, including HIV-1. Structural analysis of the VH and VL segments revealed that the natural mAb utilized three segments of the VHIV gene family and one of the VHIII family, in conjunction with VL segments of the V lambda I, V lambda II, V lambda III, or V kappa IV subgroups. In addition, the natural mAb VH and VL segments were in unmutated or virtually unmutated (germline) configuration, including those of the monoreactive mAb207.F1 to beta-galactosidase, and were identical or closely related to those utilized by specific autoantibodies or specific antibodies to viral and/or bacterial pathogens. Thus, the present data show that both polyreactive and monoreactive natural antibodies to foreign antigen can be isolated from the normal human B cell repertoire. They also suggest that the VH and VL segments of not only polyreactive but also monoreactive natural antibodies can be encoded in unmutated or minimally mutated genes, and possibly provide the templates for the specific high affinity antibodies elicited by self or foreign antigens.
致力于产生能与致病细菌和病毒上的抗原结合的抗体（天然抗体）的B淋巴细胞是正常人类B细胞库的常见组成部分。大部分天然抗体能够结合多种抗原（多反应性抗体）。利用来自三名HIV-1血清阴性健康受试者的B细胞，以及从大肠杆菌中纯化的HIV-1和β-半乳糖苷酶作为选择抗原，我们产生了三种针对HIV-1的天然IgM单克隆抗体和一种针对β-半乳糖苷酶的天然IgM单克隆抗体。三种经HIV-1选择的抗体（单克隆抗体102、单克隆抗体103和单克隆抗体104）具有多反应性。它们以不同亲和力（解离常数Kd = 10⁻⁶至10⁻⁸ M）与HIV-1包膜糖蛋白gp160、p24核心蛋白和p66逆转录酶结合，但不与120糖基化包膜蛋白结合。它们还与β-半乳糖苷酶（解离常数约为10⁻⁷ M）、破伤风类毒素以及各种自身抗原结合。相比之下，选择用于与β-半乳糖苷酶结合的天然单克隆抗体（单克隆抗体207.F1）具有单反应性，即它以高亲和力（解离常数<10⁻⁸ M）与该抗原结合，但不与测试的其他任何抗原结合，包括HIV-1。对重链可变区（VH）和轻链可变区（VL）片段的结构分析表明，天然单克隆抗体利用了VHIV基因家族的三个片段和VHIII家族的一个片段，以及VλI（V lambda I）、VλII（V lambda II）、VλIII（V lambda III）或VκIV（V kappa IV）亚组的VL片段。此外，天然单克隆抗体的VH和VL片段处于未突变或几乎未突变（种系）的构型，包括针对β-半乳糖苷酶的单反应性单克隆抗体207.F1的片段，并且与特定自身抗体或针对病毒和/或细菌病原体的特异性抗体所利用的片段相同或密切相关。因此，目前的数据表明，针对外来抗原的多反应性和单反应性天然抗体均可从正常人类B细胞库中分离得到。它们还表明，不仅多反应性天然抗体，而且单反应性天然抗体的VH和VL片段都可以由未突变或极少突变的基因编码，并可能为自身或外来抗原引发的特异性高亲和力抗体提供模板。
