Heijnen I A, Glennie M J, van de Winkel J G
Department of Immunology and Medarex Europe, University Hospital Utrecht, The Netherlands.
Cancer Immunol Immunother. 1997 Nov-Dec;45(3-4):166-70. doi: 10.1007/s002620050424.
The class I IgG receptor (Fc gamma RI) on cytotoxic effector cells has been reported to initiate destruction of tumour cells by effector cells in vitro. We are aiming at developing an immunocompetent model to evaluate the cytotoxic capacity of human Fc gamma RI for the rejection of tumour cells in vivo. Therefore, we recently generated a transgenic mouse strain expressing human Fc gamma RI on monocytes, macrophages, and neutrophils. In these mice, the human receptor is up-regulated by granulocyte-colony-stimulating factor (G-CSF) and is able to trigger cellular responses. Subsequently, in the present study the B cell lymphoma IIA1.6 cell line is selected as a tumour target, and a human Fc gamma RI-directed antitumour bispecific antibody (bsAb) is constructed and characterized. Fab' fragments of mAb 22, which bind hFc gamma RI at an epitope that is distinct from the ligand binding site, were chemically linked to Fab' fragments of rat anti-(mMHC class II antigens) mAb M5/114, yielding bsAb 22 x M5/114. This bsAb was able to bind simultaneously to hFc gamma RI and mMHC class II antigens in a dose-dependent fashion. Binding of 22 x M5/114 to Fc gamma RI was not inhibited in the presence of human IgG. It is important to note that, MHC-class-II-expressing IIA1.6 lymphoma cells were lysed by whole blood from G-CSF-treated transgenic mice in the presence of bsAb 22 x M5/114. No lysis by whole blood from non-transgenic mice or from transgenic animals that had not received G-CSF was observed. These results indicate that human Fc gamma RI is able to mediate lysis of murine IIA1.6 lymphoma cells by transgenic effector cells via bsAb 22 x M5/114. A trial with transgenic mice, evaluating the efficacy of these hFc gamma RI-directed bsAb in combination with G-CSF for treatment of IIA1.6 B cell lymphoma, is currently in progress.
据报道，细胞毒性效应细胞上的I类IgG受体（FcγRI）可在体外启动效应细胞对肿瘤细胞的破坏。我们旨在开发一种免疫活性模型，以评估人FcγRI在体内排斥肿瘤细胞的细胞毒性能力。因此，我们最近培育出了一种在单核细胞、巨噬细胞和中性粒细胞上表达人FcγRI的转基因小鼠品系。在这些小鼠中，人受体可被粒细胞集落刺激因子（G-CSF）上调，并能够触发细胞反应。随后，在本研究中，选择B细胞淋巴瘤IIA1.6细胞系作为肿瘤靶点，并构建和表征了一种人FcγRI导向的抗肿瘤双特异性抗体（bsAb）。单克隆抗体22的Fab′片段在一个与配体结合位点不同的表位结合人FcγRI，将其与大鼠抗（小鼠MHC II类抗原）单克隆抗体M5/114的Fab′片段化学连接，得到双特异性抗体22×M5/114。该双特异性抗体能够以剂量依赖的方式同时结合人FcγRI和小鼠MHC II类抗原。在人IgG存在的情况下，22×M5/114与FcγRI的结合未受到抑制。需要注意的是，在双特异性抗体22×M5/114存在的情况下，表达MHC II类分子的IIA1.6淋巴瘤细胞被来自G-CSF处理的转基因小鼠的全血裂解。未观察到来自非转基因小鼠或未接受G-CSF的转基因动物的全血产生裂解作用。这些结果表明，人FcγRI能够通过双特异性抗体22×M5/114介导转基因效应细胞对小鼠IIA1.6淋巴瘤细胞的裂解。目前正在进行一项使用转基因小鼠的试验，评估这些人FcγRI导向的双特异性抗体与G-CSF联合治疗IIA1.6 B细胞淋巴瘤的疗效。
