Ratner A, Clark W R
Department of Anatomy and Cell Biology, University of California, Los Angeles 90024.
J Immunol. 1993 May 15;150(10):4303-14.
The possibility that lymphokines such as TNF-alpha produced by CD8+ CTL are responsible for acute (short term) target cell damage induced by CTL has been debated for many years. However, the slow kinetics of TNF-induced target cell death stands in sharp contrast to the rapid target cell lysis mediated by CTL. We find that cloned CD8+ CTL activated through their TCR secrete TNF-alpha. On the other hand, our cloned CTL also have a membrane form of TNF-alpha, and they kill TNF-alpha-sensitive target cells not recognized through the TCR in a slow (18-h) lytic reaction using this surface-associated TNF-alpha. There is no secreted TNF-alpha release during this interaction. Cyclosporin A and protein synthesis inhibitors block TNF-alpha secretion, but have no effect on slow lysis mediated by the CTL. On the other hand, TNF-alpha-resistant variants are greatly resistant to slow lysis, and antibodies to TNF-alpha strongly inhibit this slow lysis. Thus, although secreted TNF-alpha does not seem to be the mechanism behind slow lysis, some form of TNF-alpha, most likely the membrane-associated form, must be involved. Not only does surface TNF-alpha appear to be biologically active in these CTL, but its expression is enhanced severalfold upon activation of the CTL through the TCR. This may be important in vivo, where surface TNF-alpha could preserve the localized nature of cytolysis and endow a CTL with an additional, albeit slower, mechanism of cell lysis. Finally, we find that although activated CTL clearly use the membrane form of TNF-alpha in slow lysis, they appear not to use TNF-alpha, in any form, during acute lysis, even under conditions in which degranulation and perforin assembly are blocked.
多年来，关于CD8 + 细胞毒性T淋巴细胞（CTL）产生的诸如肿瘤坏死因子-α（TNF-α）等淋巴因子是否是CTL诱导的急性（短期）靶细胞损伤的原因一直存在争议。然而，TNF诱导的靶细胞死亡的缓慢动力学与CTL介导的快速靶细胞裂解形成鲜明对比。我们发现，通过其T细胞受体（TCR）激活的克隆CD8 + CTL分泌TNF-α。另一方面，我们克隆的CTL也具有膜形式的TNF-α，并且它们使用这种表面相关的TNF-α，在缓慢（18小时）的裂解反应中杀死未通过TCR识别的TNF-α敏感靶细胞。在此相互作用过程中没有分泌的TNF-α释放。环孢菌素A和蛋白质合成抑制剂可阻断TNF-α的分泌，但对CTL介导的缓慢裂解没有影响。另一方面，TNF-α抗性变体对缓慢裂解具有极大抗性，并且抗TNF-α抗体强烈抑制这种缓慢裂解。因此，尽管分泌的TNF-α似乎不是缓慢裂解背后的机制，但某种形式的TNF-α，很可能是膜相关形式，必定参与其中。表面TNF-α不仅在这些CTL中似乎具有生物活性，而且在通过TCR激活CTL后其表达会增强几倍。这在体内可能很重要，在体内表面TNF-α可以保持细胞溶解的局部性质，并赋予CTL一种额外的、尽管较慢的细胞裂解机制。最后，我们发现尽管活化的CTL在缓慢裂解中明显使用膜形式的TNF-α，但在急性裂解期间，即使在脱颗粒和穿孔素组装被阻断的条件下，它们似乎也不使用任何形式的TNF-α。
