Redpath S, Alam S M, Lin C M, O'Rourke A M, Gascoigne N R
Department of Immunology, The Scripps Research Institute, La Jolla, CA 92037, USA.
J Immunol. 1999 Jul 1;163(1):6-10.
Bacterial superantigens such as Staphylococcus aureus enterotoxin A (SEA) are very potent stimulators of T cells. They bind to the Vbeta region of the TCR and to MHC class II, stimulating T cells at nanomolar concentrations. Using surface plasmon resonance measurements, we find that binding between the individual components of the complex (TCR-class II, TCR-SEA, SEA-class II) is very weak, but that the stability of the trimolecular complex is considerably enhanced, reaching an affinity similar to that found for TCR interactions with MHC:peptide ligand. Thus, the potency of SEA in stimulation of T cells is not due to particularly strong affinities between the proteins, but to a cooperative effect of interactions in the TCR-SEA-MHC class II trimolecular complex that brings the kinetics into a similar range to binding of conventional Ags. This range may be the optimum for T cell activation.
诸如金黄色葡萄球菌肠毒素A（SEA）之类的细菌超抗原是非常强效的T细胞刺激剂。它们与T细胞受体（TCR）的Vβ区域以及MHC II类分子结合，在纳摩尔浓度下就能刺激T细胞。通过表面等离子体共振测量，我们发现复合物的各个组分之间（TCR - MHC II类分子、TCR - SEA、SEA - MHC II类分子）的结合非常弱，但三分子复合物的稳定性显著增强，达到了与TCR与MHC:肽配体相互作用相似的亲和力。因此，SEA刺激T细胞的效力并非源于蛋白质之间特别强的亲和力，而是源于TCR - SEA - MHC II类分子三分子复合物中相互作用的协同效应，这种协同效应使动力学处于与传统抗原结合相似的范围。这个范围可能是T细胞激活的最佳范围。
