Webb S R, Okamoto A, Sprent J
Department of Immunology, Scripps Clinic, La Jolla, CA 92037.
J Immunol. 1988 Sep 15;141(6):1828-34.
To see k information on T cell recognition of Mlsa determinants, hybridomas were prepared from a well-characterized F23.2+ (V beta 8.2+) T cell clone specific for three different ligands, i.e., 1) Mlsa determinants, 2) fowl gamma-globulin (F gamma G) plus self-H-2 (H-2d), and 3) allo-H-2, e.g., H-2p, determinants. Fusion of the clone to the BW5147 thymoma line produced a triple-reactive T hybridoma which generated two types of spontaneous variants. One type of variant (type I) lost Mlsa reactivity but retained reactivity to both F gamma G/H-2d and allo-H-2p. These variants, which were generated at high frequency, stained strongly with a mAb, A1.57, with idiotypic specificity for the TCR molecules of the parental clone. The second type of variant (type II) reacted to Mlsa determinants but showed no reactivity to F gamma G/H-2d or to allo-H-2p. These variants failed to express the A1.57 idiotypic determinants of the parent clone, but were F23.2+ (V beta 8.2+); nonequilibrium pH gradient electrophoresis analysis suggested that these hybrids expressed a mixed TCR heterodimer composed of the parental clone beta-chain and the BW5147 alpha-chain. Three aspects of the data are very difficult to accommodate with the view that Mlsa, F gamma G, and allo-H-2 determinants are all recognized via a common TCR molecule: 1) the independent (and frequent) segregation of Mlsa reactivity from F gamma G/H-2d and allo-H-2p reactivity, 2) the retention of Mlsa reactivity by the type II variants despite loss of the parental clone alpha-chain, and 3) the loss of Mlsa reactivity by the type I variants despite high expression of the A1.57+ TcR molecules derived from the parental clone. The data support a model in which Mlsa determinants are recognized by a separate T cell structure, which we envisage as a monomorphic accessory molecule unrelated to the TCR. Since the type II hybridoma variants invariably retained quantitatively normal TcR expression, the triggering phase of anti-Mlsa responses appears to be TCR dependent. The model we favor is that anti-Mlsa/Mlsa interaction increases TCR binding with Ia epitopes to above the threshold required for cell triggering. A key feature of this model is that Mlsa and Ia determinants are recognized as separate structures rather than as a complex.
为获取有关T细胞对Mlsa决定簇识别的信息，用一个特征明确的F23.2+(Vβ8.2+)T细胞克隆制备杂交瘤，该克隆对三种不同配体具有特异性，即：1) Mlsa决定簇；2) 鸡γ球蛋白(FγG)加自身H-2(H-2d)；3) 同种异体H-2，如H-2p决定簇。将该克隆与BW5147胸腺瘤细胞系融合产生了一种三反应性T杂交瘤，它产生了两种自发变体。一种变体（I型）丧失了对Mlsa的反应性，但保留了对FγG/H-2d和同种异体H-2p的反应性。这些高频产生的变体用单克隆抗体A1.57强烈染色，该抗体对亲本克隆的TCR分子具有独特型特异性。第二种变体（II型）对Mlsa决定簇有反应，但对FγG/H-2d或同种异体H-2p无反应。这些变体未能表达亲本克隆的A1.57独特型决定簇，但为F23.2+(Vβ8.2+)；非平衡pH梯度电泳分析表明，这些杂交瘤表达了一种由亲本克隆的β链和BW5147的α链组成的混合TCR异二聚体。数据中的三个方面很难与Mlsa、FγG和同种异体H-2决定簇均通过共同的TCR分子被识别这一观点相契合：1) Mlsa反应性与FγG/H-2d和同种异体H-2p反应性的独立（且频繁）分离；2) II型变体尽管亲本克隆的α链缺失，但仍保留了对Mlsa的反应性；3) I型变体尽管高表达源自亲本克隆的A1.57+TCR分子，但仍丧失了对Mlsa的反应性。这些数据支持一种模型，即Mlsa决定簇由一种单独的T细胞结构识别，我们设想它是一种与TCR无关的单态辅助分子。由于II型杂交瘤变体始终保持定量正常的TCR表达，抗Mlsa反应的触发阶段似乎是TCR依赖性的。我们支持的模型是，抗Mlsa/Mlsa相互作用使TCR与Ia表位的结合增加到细胞触发所需的阈值以上。该模型的一个关键特征是，Mlsa和Ia决定簇被识别为单独的结构，而不是一个复合物。
