Kinoshita T, Thyphronitis G, Tsokos G C, Finkelman F D, Hong K, Sakai H, Inoue K
Department of Bacteriology, Osaka University Medical School, Japan.
Int Immunol. 1990;2(7):651-9. doi: 10.1093/intimm/2.7.651.
We have previously demonstrated that some mAbs prepared against mouse complement receptor type 1 (CR1) bind a 150,000 Mr protein in addition to the 190,000 Mr CR1 protein. We now identify the 150,000 Mr murine protein as complement receptor type 2 (CR2), since: (i) one of the monoclonal antibodies that bind this protein inhibits rosette formation between mouse B cells and C3d-bearing sheep erythrocytes; (ii) as is known for human CR2, this protein is present on B lymphocytes but not T lymphocytes; and (iii) this protein must have affinity for C3b, since it has weak factor I cofactor activity. In addition, this protein resembles the 145,000 Mr human CR2 molecule in size. Since four of the five mAbs that were produced by immunization with CR1 also bound CR2, and they bind to different CR1 epitopes, it seems that murine CR1 and CR2 share multiple epitopes. Injection of mice with one of the CR1-CR2 cross-reactive mAbs almost eliminated both CR1 and CR2 expression, but did not decrease B cell numbers or the expression of B cell IgM, Ia, or B220 antigens. In contrast, injection of mice with a non-cross-reactive anti-CR1 antibody only modulated CR1 expression. These antibodies should thus provide useful tools for the study of the in vivo roles of B cell complement receptors.
我们之前已证明，一些针对小鼠1型补体受体（CR1）制备的单克隆抗体（mAb），除了能结合190,000 Mr的CR1蛋白外，还能结合一种150,000 Mr的蛋白。我们现在确定这种150,000 Mr的小鼠蛋白为2型补体受体（CR2），原因如下：（i）一种能结合该蛋白的单克隆抗体可抑制小鼠B细胞与携带C3d的绵羊红细胞之间的玫瑰花结形成；（ii）正如人CR2的情况一样，该蛋白存在于B淋巴细胞而非T淋巴细胞上；（iii）该蛋白必定对C3b有亲和力，因为它具有较弱的I因子辅因子活性。此外，这种蛋白在大小上与145,000 Mr的人CR2分子相似。由于用CR1免疫产生的5种mAb中有4种也能结合CR2，且它们结合不同的CR1表位，所以小鼠CR1和CR2似乎共享多个表位。给小鼠注射一种CR1 - CR2交叉反应性mAb几乎消除了CR1和CR2的表达，但并未减少B细胞数量或B细胞IgM、Ia或B220抗原的表达。相比之下，给小鼠注射一种非交叉反应性抗CR1抗体只会调节CR1的表达。因此，这些抗体应为研究B细胞补体受体在体内的作用提供有用的工具。
