Wargalla U C, Reisfeld R A
Department of Immunology, Research Institute of Scripps Clinic, La Jolla, CA 92037.
Proc Natl Acad Sci U S A. 1989 Jul;86(13):5146-50. doi: 10.1073/pnas.86.13.5146.
The relationship between the cellular internalization of an anti-ganglioside GD2 monoclonal antibody (14.G2a) and the toxic effect of its ricin A-chain immunotoxin (14.G2a-RA) was examined on GD2-bearing M21 human melanoma and T293 small cell lung carcinoma cell lines. The capacity for ligand uptake was determined by examining the parameters that contribute to this constant, including the number of cell-surface binding sites and the internalization rate constant (ke). The maximum uptake of 14.G2a is 11-fold greater for M21 than for T293 cells, due to a 2.7-fold difference in binding sites and a 4-fold difference in the rate of antibody internalization. The capacity for ligand uptake correlates with the cytotoxic activity of the 14.G2a-RA immunotoxin against these two cell lines. Furthermore, we were able to demonstrate that the consequence of internalization of 14.G2a-RA is the intracellular release of undegraded ricin A-chain from the antibody. These studies indicate that the rate of internalization is a quantitative parameter that plays a key role in predicting the cytotoxic potency of this immunotoxin.
在携带GD2的M21人黑色素瘤细胞系和T293小细胞肺癌细胞系上，研究了抗神经节苷脂GD2单克隆抗体（14.G2a）的细胞内化与其蓖麻毒素A链免疫毒素（14.G2a-RA）毒性作用之间的关系。通过检测有助于维持这一常数的参数，包括细胞表面结合位点的数量和内化速率常数（ke），来确定配体摄取能力。由于结合位点存在2.7倍的差异以及抗体内化速率存在4倍的差异，14.G2a在M21细胞中的最大摄取量比在T293细胞中高11倍。配体摄取能力与14.G2a-RA免疫毒素对这两种细胞系的细胞毒性活性相关。此外，我们能够证明14.G2a-RA内化的结果是未降解的蓖麻毒素A链从抗体中释放到细胞内。这些研究表明，内化速率是一个定量参数，在预测这种免疫毒素的细胞毒性效力方面起着关键作用。
