Brooks C G, Holscher M, Urdal D
J Immunol. 1985 Aug;135(2):1145-52.
It has previously been shown that monoclonal antigen-specific mouse CTL lines can be induced to express cytolytic activity with the same specificity as that of splenic natural killer (NK) cells following culture in high concentrations of concanavalin A-induced spleen cell supernatants. In the present experiments, we made use of this in vitro system to explore the regulation of NK activity at the clonal level. Interferon-alpha and interferon-beta and interleukin 2 (IL 2) were potent inducers of NK activity in CTL, demonstrating that these substances can activate NK functions directly without the participation of other cell types. By comparison, IFN-gamma was a poor activator of NK activity in CTL (and also in fresh spleen cells). Three major differences between induction of NK activity by IFN-alpha,beta and IL 2 were noted: IFN induced NK activity selectively without affecting specific cytolysis, whereas IL 2 also enhanced specific killing; IFN acted much more rapidly than IL 2; and IFN did not induce the cells to enter the cell cycle nor were there any obvious morphologic changes. Specific antigen was also a strong inducer of NK activity in CTL, but studies with antisera against the various classes of IFN revealed that this effect was mediated, at least in part, via the release of IFN-beta. By contrast, the same antisera had no effect on NK induction by crude TCGF or by highly purified IL 2, indicating that the regulation of NK activity by IL 2 occurs at the clonal level in an IFN-independent manner. Although, IL 2, IFN, and Ag could apparently act alone to induce NK activity, much greater (synergistic) induction was obtained by various combinations of these regulators, suggesting that the delivery of two (or more) signals to the responder cell was required for full expression of the NK state. As with fresh splenic NK cells, the induced NK state in cloned CTL was intrinsically labile as revealed by its rapid decay in the absence of inducers, but it could nonetheless be maintained indefinitely at very high levels in the continued presence of inducers. This clonal system thus displays a responsiveness to regulatory signals exactly analogous to that of splenic NK cells and provides a unique and exciting opportunity to evaluate the biochemistry of the regulation of NK activity.
先前已经表明，在高浓度伴刀豆球蛋白A诱导的脾细胞上清液中培养后，单克隆抗原特异性小鼠CTL系可被诱导表达与脾自然杀伤（NK）细胞相同特异性的细胞溶解活性。在本实验中，我们利用这个体外系统在克隆水平上探索NK活性的调节。α干扰素、β干扰素和白细胞介素2（IL-2）是CTL中NK活性的有效诱导剂，表明这些物质可直接激活NK功能，而无需其他细胞类型的参与。相比之下，γ干扰素在CTL（以及新鲜脾细胞）中是NK活性的较差激活剂。注意到α干扰素、β干扰素和IL-2诱导NK活性之间的三个主要差异：干扰素选择性诱导NK活性而不影响特异性细胞溶解，而IL-2也增强特异性杀伤；干扰素的作用比IL-2快得多；并且干扰素不会诱导细胞进入细胞周期，也没有任何明显的形态学变化。特异性抗原也是CTL中NK活性的强诱导剂，但用针对各类干扰素的抗血清进行的研究表明，这种效应至少部分是通过β干扰素的释放介导的。相比之下，相同的抗血清对粗制TCGF或高度纯化的IL-2诱导的NK活性没有影响，表明IL-2对NK活性的调节以不依赖干扰素的方式在克隆水平上发生。虽然IL-2、干扰素和抗原显然可以单独作用诱导NK活性，但这些调节剂的各种组合可获得更大（协同）的诱导效果，这表明向反应细胞传递两个（或更多）信号是NK状态充分表达所必需的。与新鲜脾NK细胞一样，克隆的CTL中诱导的NK状态本质上是不稳定的，这可通过其在无诱导剂时的快速衰减看出，但在持续存在诱导剂的情况下，它仍可在非常高的水平上无限期维持。因此，这个克隆系统显示出对调节信号的反应性与脾NK细胞完全类似，并提供了一个独特且令人兴奋的机会来评估NK活性调节的生物化学。
