Adolf G R, Frühbeis B
Department of Cell Biology, Ernst Boehringer-Institut für Arzneimittelforschung, Bender + Co Ges mbH, Vienna, Austria.
Cytokine. 1992 May;4(3):180-4. doi: 10.1016/1043-4666(92)90053-t.
A soluble extracellular fragment of the human 55-60 kDa tumor necrosis factor receptor (sTNF-R I), originally isolated from urine, binds both TNF-alpha and TNF-beta and blocks the activity of these cytokines in biological assays. Three monoclonal antibodies (mAbs) raised against sTNF-R I (TBP-1, -2 and -6) as well as a mAb developed by immunization with the intact receptor (H398) were analysed for their epitope specificities in ELISAs and for biological activity in cytotoxicity assays on murine L-M cells. TBP-2 and H398 bind to related epitopes on sTNF-R I; they compete with TNF-alpha for binding and block the protective effect of sTNF-R I in the bioassay. MAbs TBP-1 and TBP-6 recognize two further, independent epitopes; both bind sTNF-R I in the presence of an excess of TNF-alpha. Both TBP-1 and TBP-6 markedly enhance the ability of sTNF-R I to protect cells against the cytotoxic activities of TNF-alpha and TNF-beta, but have no activity in the absence of sTNF-R I. Fab fragments show much lower activity. We propose that the ability of certain mAbs to enhance the protective activity of sTNF-R is due to a steric hindrance phenomenon.
人55 - 60 kDa肿瘤坏死因子受体（sTNF - R I）的可溶性细胞外片段最初从尿液中分离得到，它能结合TNF -α和TNF -β，并在生物学检测中阻断这些细胞因子的活性。分析了三种针对sTNF - R I产生的单克隆抗体（mAb，TBP - 1、- 2和 - 6）以及一种用完整受体免疫制备的单克隆抗体（H398）在酶联免疫吸附测定（ELISA）中的表位特异性，以及在小鼠L - M细胞的细胞毒性检测中的生物学活性。TBP - 2和H398结合sTNF - R I上的相关表位；它们与TNF -α竞争结合，并在生物检测中阻断sTNF - R I的保护作用。单克隆抗体TBP - 1和TBP - 6识别另外两个独立的表位；在TNF -α过量存在时，它们都能结合sTNF - R I。TBP - 1和TBP - 6都显著增强sTNF - R I保护细胞免受TNF -α和TNF -β细胞毒性作用的能力，但在没有sTNF - R I时没有活性。Fab片段的活性要低得多。我们认为某些单克隆抗体增强sTNF - R保护活性的能力是由于空间位阻现象。
