Link B K, Kostelny S A, Cole M S, Fusselman W P, Tso J Y, Weiner G J
Department of Internal Medicine, University of Iowa Cancer Center, University of Iowa College of Medicine, Iowa City, USA.
Int J Cancer. 1998 Jul 17;77(2):251-6. doi: 10.1002/(sici)1097-0215(19980717)77:2<251::aid-ijc14>3.0.co;2-e.
Anti-CD3 x anti-B-cell antigen bispecific monoclonal antibodies (bsAbs) can redirect T-cell-mediated lysis toward malignant B cells. Clinical trials with CD3-based bsAbs have shown toxicity in patients which is likely related to nonspecific T-cell activation and targeting. Our current studies were designed to explore the mechanisms responsible for the observed in vivo toxicity by evaluating the immunologic effects of 2 different bsAb preparations in vitro. 1D10 was used as the tumor specific arm of the bsAbs. This antibody reacts with a variant of HLA-DR found on a majority of pre-B- and B-cell malignancies, and normal B cells in some individuals. Anti-CD3 served as the T-cell specific arm. A 1D10 x anti-CD3 bispecific IgG (bsIgG) produced using the hybrid-hybridoma method was compared to a 1D10 x anti-CD3 bispecific F(ab')2 [bsF(ab')2] produced using the leucine zipper technique. In cytotoxicity assays, both bsIgG and bsF(ab')2 induced lysis by pre-activated T cells of 1D10 (+) malignant B cells. bsIgG at high concentrations also induced lysis of 1D10 (-) tumor cells, while bsF(ab')2 did not. Proliferation of T cells induced by bsIgG and bsF(ab')2 was also evaluated. Both forms of bsAbs induced T-cell proliferation in the presence of antigen (+) Raji cells, while only bsIgG did so in the presence of antigen (-) malignant B cells. bsF(ab')2 induced T-cell activation in the absence of any tumor cells when testing was performed on samples where the 1D10 target antigen was present on normal peripheral blood B cells. We conclude that non-specific T-cell activation from bsAbs can occur in an antigen-independent manner due to the Fc/Fc receptor (FcR) interaction, or in an antigen-dependent manner when antigen is expressed on normal or tumor cells. Both mechanisms may have been responsible for the toxicity observed in prior clinical studies.
抗CD3×抗B细胞抗原双特异性单克隆抗体（bsAbs）可使T细胞介导的细胞溶解作用重新导向恶性B细胞。基于CD3的bsAbs的临床试验已显示对患者具有毒性，这可能与非特异性T细胞活化和靶向作用有关。我们当前的研究旨在通过评估两种不同bsAb制剂在体外的免疫效应，来探究导致观察到的体内毒性的机制。1D10用作bsAbs的肿瘤特异性臂。该抗体与在大多数前B细胞和B细胞恶性肿瘤以及某些个体的正常B细胞上发现的HLA-DR变体发生反应。抗CD3用作T细胞特异性臂。将使用杂交-杂交瘤方法产生的1D10×抗CD3双特异性IgG（bsIgG）与使用亮氨酸拉链技术产生的1D10×抗CD3双特异性F(ab')2 [bsF(ab')2]进行比较。在细胞毒性试验中，bsIgG和bsF(ab')2均诱导预激活的T细胞对1D10(+)恶性B细胞进行细胞溶解。高浓度的bsIgG还诱导对1D10(-)肿瘤细胞的细胞溶解，而bsF(ab')2则不会。还评估了bsIgG和bsF(ab')2诱导的T细胞增殖。两种形式的bsAbs在存在抗原(+)的Raji细胞时均诱导T细胞增殖，而仅bsIgG在存在抗原(-)的恶性B细胞时诱导T细胞增殖。当对正常外周血B细胞上存在1D10靶抗原的样品进行检测时，bsF(ab')2在不存在任何肿瘤细胞的情况下诱导T细胞活化。我们得出结论，bsAbs的非特异性T细胞活化可能由于Fc/ Fc受体（FcR）相互作用而以抗原非依赖性方式发生，或者当抗原在正常或肿瘤细胞上表达时以抗原依赖性方式发生。这两种机制可能都与先前临床研究中观察到的毒性有关。
