Van Seventer G A, Bonvini E, Yamada H, Conti A, Stringfellow S, June C H, Shaw S
Experimental Immunology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892.
J Immunol. 1992 Dec 15;149(12):3872-80.
Activation of resting human CD4+ T cells mediated by mAb ligation of the TCR/CD3 complex requires costimulatory signals to result in proliferation; these can be provided by intercellular cell adhesion molecule-1 (ICAM-1, CD54) a natural ligand of leukocyte function-associated Ag-1 (LFA-1, CD11a/CD18). We analyzed early signaling events involved in T cell activation to determine the contribution by the LFA-1/ICAM-1 interaction. We studied in detail the hydrolysis of phosphatidylinositol(4,5)bisphosphate and intracellular levels of free Ca2+ during stimulation with beads coated with the CD3 mAb OKT3 alone or in combination with purified ICAM-1 protein. Our investigations show no response to LFA-1/ICAM-1 alone, but that costimulation by LFA-1/CAM-1 interaction induces prolonged inositol phospholipid hydrolysis (up to 4 h), resulting in generation of both inositol(1,4,5)phosphate3 and inositol(1,3,4,5)phosphate4 and their derivatives. Based on studies with cycloheximide, this costimulatory effect of prolonged inositol phospholipid hydrolysis appears dependent in part on de novo protein synthesis. A sustained increase in intracellular levels of free Ca2+ level is also observed after LFA-1/ICAM-1 costimulation, which is at least partly dependent on extracellular sources of Ca2+. Kinetic studies indicate that costimulation requires a minimal period of 4 h of LFA-1/ICAM-1 interaction to provide maximal costimulation for OKT3-mediated T cell proliferation. Thus, the necessary costimulation required for OKT3-mediated proliferation in this model system may be provided by an extended LFA-1/ICAM-1 interaction that in combination with OKT3 mAb leads to signal-transducing events, resulting in prolonged phospholipase C activation and phosphatidylinositol(4,5)bisphosphate hydrolysis, and a sustained increase in intracellular levels of free Ca2+.
通过TCR/CD3复合物的单克隆抗体连接介导的静息人CD4 + T细胞激活需要共刺激信号才能导致增殖；这些信号可由细胞间黏附分子-1（ICAM-1，CD54）提供，ICAM-1是白细胞功能相关抗原-1（LFA-1，CD11a/CD18）的天然配体。我们分析了T细胞激活过程中涉及的早期信号事件，以确定LFA-1/ICAM-1相互作用的贡献。我们详细研究了单独用包被有CD3单克隆抗体OKT3或与纯化的ICAM-1蛋白联合刺激期间磷脂酰肌醇（4,5）二磷酸的水解和细胞内游离Ca2+水平。我们的研究表明，单独的LFA-1/ICAM-1无反应，但LFA-1/CAM-1相互作用的共刺激可诱导延长的肌醇磷脂水解（长达4小时），导致肌醇（1,4,5）三磷酸和肌醇（1,3,4,5）四磷酸及其衍生物的生成。基于用放线菌酮的研究，延长的肌醇磷脂水解的这种共刺激作用似乎部分依赖于从头合成蛋白质。在LFA-1/ICAM-1共刺激后也观察到细胞内游离Ca2+水平的持续升高，这至少部分依赖于细胞外Ca2+来源。动力学研究表明，共刺激需要至少4小时的LFA-1/ICAM-1相互作用期，才能为OKT3介导的T细胞增殖提供最大共刺激。因此，在该模型系统中OKT3介导的增殖所需的必要共刺激可能由延长的LFA-1/ICAM-1相互作用提供，该相互作用与OKT3单克隆抗体联合导致信号转导事件，导致磷脂酶C持续激活和磷脂酰肌醇（4,5）二磷酸水解，以及细胞内游离Ca2+水平的持续升高。
