Dantal J, Jacques Y, Soulillou J P
National Institute of Health and Research, INSERM U211, University of Nantes, France.
Transplantation. 1991 Jul;52(1):110-5. doi: 10.1097/00007890-199107000-00023.
Monoclonal antibodies directed against the P55 component of the interleukin 2 receptor (IL-2-R) have been used to prevent allograft rejection in various animal models, including primates and man. This study compares the functional effects of seven MoAbs directed against the mouse IL-2-R P55 chain both in vitro using the mouse CTL-L2 cell line and in vivo in a sheep red blood cell-induced delayed-type hypersensitivity model. Data from in vitro studies showed that a cluster of four MoAbs (cluster I: 5A2, 125, 135 [IgG2a] and AMT13 [IgG2b]) competed with IL-2 for binding to the P55 chain and caused an inhibition of IL-2-induced proliferation on CTL-L2. The respective dissociation constants (Kd) of the four MoAbs were 1.1, 1.4, 2.5, and 5.5 nM, and they all displayed a common maximal binding capacity of 2 x 10(5) sites per cell on CTL-L2. None of these MoAbs were found to fix rabbit complement. The three other MoAbs (2E4: IgG2a, 7D4: IgM, PC61: IgG1) with respective Kd of 0.8, 0.2, and 0.85 nM and maximal binding capacities of 2 x 10(5), 4 x 10(5) sites per cell did not interfere with IL-2 binding and did not affect the IL-2-induced proliferation of the murine cell line. All three MoAbs were found to define three separate epitopic clusters independent of cluster I. Among them, only 2E4 induced a strong complement-mediated cytotoxicity. In vivo experiments showed that all MoAbs from cluster I were efficient in suppressing the DTH reaction and that the magnitude of their effect was consistent with their respective Kds. At a suboptimal dose of 1 microgram per day, the DTH inhibition indices were 40%, 43%, 23%, and 9% for 5A2, 125, 135, and AMT13, respectively. The 2E4 MoAb was found to be as efficient as cluster I MoAbs in suppressing DTH (53% inhibition at 1 microgram/day) while 7D4 and PC61 induced only a moderate inhibitory effect (37% inhibition for each MoAb given at 10 micrograms/day, compared with 70% inhibition for cluster I MoAbs). Taken together, our results indicate that blocking the IL-2/IL-2-R interaction without complement fixation is sufficient per se to attenuate the DTH reaction, and conversely that strong complement-mediated cytotoxicity in the absence of a functional effect in the IL-2/IL-2-R interaction is also effective in this system. Finally, no synergistic effect between MoAbs belonging to different clusters was evidenced in the DTH model.
针对白细胞介素2受体（IL-2-R）P55成分的单克隆抗体已被用于预防包括灵长类动物和人类在内的各种动物模型中的同种异体移植排斥反应。本研究比较了七种针对小鼠IL-2-R P55链的单克隆抗体在体外使用小鼠CTL-L2细胞系以及在体内绵羊红细胞诱导的迟发型超敏反应模型中的功能效应。体外研究数据表明，一组四种单克隆抗体（第一组：5A2、125、135 [IgG2a] 和AMT13 [IgG2b]）与IL-2竞争结合P55链，并抑制IL-2诱导的CTL-L2细胞增殖。这四种单克隆抗体各自的解离常数（Kd）分别为1.1、1.4、2.5和5.5 nM，它们在CTL-L2细胞上均显示出每细胞2×10⁵个位点的共同最大结合能力。未发现这些单克隆抗体能固定兔补体。另外三种单克隆抗体（2E4：IgG2a、7D4：IgM、PC61：IgG1），其Kd分别为0.8、0.2和0.85 nM，最大结合能力分别为每细胞2×10⁵、4×10⁵个位点，不干扰IL-2结合，也不影响IL-2诱导的小鼠细胞系增殖。发现所有这三种单克隆抗体定义了三个独立于第一组的不同表位簇。其中，只有2E4诱导强烈的补体介导的细胞毒性。体内实验表明，第一组的所有单克隆抗体在抑制迟发型超敏反应方面均有效，其效应程度与各自的Kd一致。在每天1微克的次优剂量下，5A2、125、135和AMT13的迟发型超敏反应抑制指数分别为40%、43%、23%和9%。发现2E4单克隆抗体在抑制迟发型超敏反应方面与第一组单克隆抗体一样有效（每天1微克时抑制53%），而7D4和PC61仅诱导中等抑制作用（每种单克隆抗体每天给予10微克时抑制37%，而第一组单克隆抗体为70%）。综上所述，我们的结果表明，在不固定补体的情况下阻断IL-2/IL-2-R相互作用本身足以减弱迟发型超敏反应，相反，在IL-2/IL-2-R相互作用中无功能效应的情况下强烈的补体介导的细胞毒性在该系统中也有效。最后，在迟发型超敏反应模型中未证明属于不同簇的单克隆抗体之间有协同作用。
