Lambert L E, Paulnock D M
Department of Medical Microbiology, University of Wisconsin Medical School, Madison 53706.
J Immunol. 1987 Oct 15;139(8):2834-41.
Macrophage activation for tumor cell killing is a multistep pathway in which responsive macrophages interact sequentially with priming and triggering stimuli in the acquisition of full tumoricidal activity. Although this synergistic response of normal macrophages to sequential incubation with activation signals has been well established, characterization of the intermediate stages in this pathway has been difficult, due in large measure to the instability of the intermediate cell phenotypes. We have developed a model system for examination of macrophage-mediated tumor cell lysis, with the use of the murine macrophage tumor cell line RAW 264.7. These cells, like normal macrophages, exhibit a strict requirement for interaction with both interferon-gamma (IFN-gamma, the priming signal) and bacterial lipopolysaccharide (LPS, the triggering signal) in the development of tumor cytolytic activity. In this system, the priming effects of IFN-gamma decay rapidly after withdrawal of this mediator and the cells become unresponsive to LPS triggering. We have recently observed that gamma-irradiation of the RAW 264.7 cells also results in development of a primed activation state for tumor cell killing. The effects of gamma-radiation on the RAW 264.7 cell line are strikingly similar to those resulting from incubation with IFN-gamma, with the exception that the irradiation-induced primed cell intermediate is stable and responsive to LPS triggering for at least 24 hr. Treatment with gamma-radiation also results in increased cell surface expression of major histocompatibility complex-encoded class I antigens; however, class II antigen expression is not induced. Irradiation-induced development of the primed phenotype is not solely the result of cytostatic effects as treatment of the cells with a radiomimetic drug, mitomycin C, results in decreases in [3H]thymidine incorporation that are similar to those observed after irradiation, without concomitant development of cytolytic potential. In addition, priming by gamma-radiation does not appear to be mediated by the release of soluble autoregulatory factors. This alternate pathway for induction of the primed macrophage activation state should serve as a useful tool for identification of molecules important to the functional potential of primed cells, and for elucidation of the biochemical mechanisms of the priming event in tumoricidal activation.
巨噬细胞被激活以杀伤肿瘤细胞是一个多步骤过程，在此过程中，有反应性的巨噬细胞在获得完全的杀肿瘤活性时，会依次与启动刺激和触发刺激相互作用。尽管正常巨噬细胞对激活信号进行顺序孵育时的这种协同反应已得到充分证实，但由于中间细胞表型的不稳定性，该途径中间阶段的特征一直难以确定。我们利用小鼠巨噬细胞瘤细胞系RAW 264.7开发了一个用于检测巨噬细胞介导的肿瘤细胞裂解的模型系统。这些细胞与正常巨噬细胞一样，在肿瘤细胞溶解活性的发展过程中，对与干扰素-γ（IFN-γ，启动信号）和细菌脂多糖（LPS，触发信号）的相互作用都有严格要求。在这个系统中，撤去IFN-γ后，其启动效应会迅速衰减，细胞对LPS触发变得无反应。我们最近观察到，对RAW 264.7细胞进行γ射线照射也会导致其进入用于杀伤肿瘤细胞的启动激活状态。γ射线对RAW 264.7细胞系的影响与用IFN-γ孵育产生的影响惊人地相似，不同之处在于，照射诱导的启动细胞中间体是稳定的，并且对LPS触发至少24小时有反应。用γ射线处理还会导致主要组织相容性复合体编码的I类抗原在细胞表面的表达增加；然而，不会诱导II类抗原的表达。照射诱导的启动表型的形成并非仅仅是细胞生长抑制作用的结果，因为用一种放射模拟药物丝裂霉素C处理细胞会导致[3H]胸腺嘧啶核苷掺入量的减少，这与照射后观察到的情况相似，但不会伴随细胞溶解潜能的发展。此外，γ射线引发似乎不是由可溶性自调节因子的释放介导的。这种诱导启动巨噬细胞激活状态的替代途径应成为一种有用的工具，用于鉴定对启动细胞功能潜能重要的分子，并阐明杀肿瘤激活中启动事件的生化机制。
