Koch C, Staffler G, Hüttinger R, Hilgert I, Prager E, Cerný J, Steinlein P, Majdic O, Horejsí V, Stockinger H
Institute of Immunology-Vienna International Research Cooperation Center at NFI, University of Vienna, Brunner Strasse 59, 1235 Vienna, Austria.
Int Immunol. 1999 May;11(5):777-86. doi: 10.1093/intimm/11.5.777.
CD147 is a broadly expressed cell surface glycoprotein of the Ig superfamily whose expression is up-regulated upon T cell activation. In order to elucidate a possible role of CD147 in T cell biology, we established 15 specific mAb. Seven distinct epitopes were defined by the mAb panel. Most of the mAb bound only to phytohemagglutinin (PHA)-activated but not resting T cells. We demonstrate that this was not because of true expression of activation-dependent neoepitopes but rather due to bivalent binding of the relatively low-affinity mAb (affinity constant KA values between 2.25 x 10(8) and 7 x 10(9) M-1) to the more densely expressed and/or more clustered CD147 molecules on the activated T cells. In contrast, the mAb with higher affinity (KA > 7 x 10(9) M-1) could stably bind in a monovalent fashion even to the relatively low dense CD147 molecules on resting T cells. This model might more generally explain the nature of 'activation epitopes' described previously in other leukocyte surface molecules. Finally, we provide evidence that induction of ordered dimerization of CD147 by a mAb directed to a unique epitope results in strong inhibition of CD3-mediated T cell activation.
CD147是免疫球蛋白超家族中一种广泛表达的细胞表面糖蛋白，其表达在T细胞活化时上调。为了阐明CD147在T细胞生物学中的可能作用，我们制备了15种特异性单克隆抗体。单克隆抗体组定义了7个不同的表位。大多数单克隆抗体仅与植物血凝素（PHA）激活的T细胞结合，而不与静息T细胞结合。我们证明，这不是因为激活依赖性新表位的真实表达，而是由于相对低亲和力的单克隆抗体（亲和力常数KA值在2.25×10⁸至7×10⁹M⁻¹之间）与活化T细胞上表达更密集和/或聚集程度更高的CD147分子发生二价结合。相反，具有更高亲和力（KA>7×10⁹M⁻¹）的单克隆抗体甚至可以以单价方式稳定结合到静息T细胞上相对低密度的CD147分子。该模型可能更普遍地解释了先前在其他白细胞表面分子中描述的“激活表位”的性质。最后，我们提供证据表明，针对独特表位的单克隆抗体诱导CD147有序二聚化会导致CD3介导的T细胞活化受到强烈抑制。
