Riches D W, Underwood G A
Department of Pediatrics, National Jewish Center for Immunology and Respiratory Medicine, Denver, Colorado 80206.
J Biol Chem. 1991 Dec 25;266(36):24785-92.
The expression of cytocidal activity is induced by the sequential interaction of macrophages with a priming stimulus, such as interferon (IFN)alpha, -beta, or -gamma, and a triggering stimulus, such as poly(I.C) or lipopolysaccharide. However, most triggering stimuli are also capable of inducing IFN expression. This suggested to us the possibility that in addition to its role in initially priming macrophages for cytocidal activity, IFN may also be expressed during the triggering stage where it may potentially contribute to the regulation of cytocidal activity. We have explored this question by (i) attempting to dissociate IFN-inducing activity from triggering activity with a variety of structurally related and charge-related polyanions; (ii) determining if macrophages express IFN during the triggering stage; and (iii) questioning if IFN produced during the triggering stage contributes to the regulation of cytocidal activation. Exposure of unprimed macrophages to a triggering concentration of poly(I.C) alone failed to induce IFN beta expression. However, exposure of IFN beta-primed cells to poly(I.C) dramatically increased the expression of IFN beta mRNA. Priming with IFN gamma was likewise found to increase the expression of IFN beta mRNA in response to a triggering concentration of polyribonucleotides. Three approaches were adopted to ascertain if the increased expression of IFN beta contributed to cytocidal activation. First, macrophages derived from strains of mice which differ in their susceptibility to IFN induction by poly(I.C) were primed with IFN beta, washed, and triggered with poly(I.C). Under these conditions, macrophages derived from stain B10.A(2R), which are hyporesponsive to poly(I.C) in terms of IFN induction, also showed a diminished capacity to express Bf, a marker of cytocidal activation. Second, exposure of IFN-primed macrophages to poly(I.C) in the presence of anti-IFN alpha/beta antibody was found to reduce substantially the synthesis of NO2/NO3, an alternative marker of macrophage cytocidal activation. Third, exposure of IFN-primed macrophages to the calcium ionophores ionomycin or A23187, which do not induce the production of IFN beta during triggering, led to an abbreviated expression of Bf compared with stimuli that induce IFN beta expression such as poly(I.C). However, the capacity to synthesize Bf in response to A23187 was partially reconstituted when macrophages were triggered with the ionophore in the continuous presence of IFN beta. Collectively, these data show that IFN beta is expressed during the triggering stage of macrophage cytocidal activation and suggest that it plays an important and previously unsuspected role in the expression of this state.
巨噬细胞与引发刺激物（如α、β或γ干扰素）及触发刺激物（如聚肌胞苷酸或脂多糖）依次相互作用可诱导细胞杀伤活性的表达。然而，大多数触发刺激物也能够诱导干扰素表达。这使我们推测，干扰素除了在最初启动巨噬细胞的细胞杀伤活性中发挥作用外，还可能在触发阶段表达，从而可能有助于细胞杀伤活性的调节。我们通过以下方式探讨了这个问题：（i）尝试用多种结构相关和电荷相关的聚阴离子将干扰素诱导活性与触发活性分离；（ii）确定巨噬细胞在触发阶段是否表达干扰素；（iii）探究触发阶段产生的干扰素是否有助于细胞杀伤激活的调节。未启动的巨噬细胞单独暴露于触发浓度的聚肌胞苷酸时，未能诱导β干扰素表达。然而，β干扰素启动的细胞暴露于聚肌胞苷酸后，β干扰素mRNA的表达显著增加。同样发现，用γ干扰素启动可增加对触发浓度的多聚核糖核苷酸反应时β干扰素mRNA的表达。采用了三种方法来确定β干扰素表达的增加是否有助于细胞杀伤激活。首先，用β干扰素启动来自对聚肌胞苷酸诱导干扰素敏感性不同的小鼠品系的巨噬细胞，洗涤后再用聚肌胞苷酸触发。在这些条件下，来自B10.A(2R)品系的巨噬细胞，其在干扰素诱导方面对聚肌胞苷酸反应低下，在细胞杀伤激活标志物Bf的表达能力上也有所下降。其次，发现β干扰素启动的巨噬细胞在抗α/β干扰素抗体存在下暴露于聚肌胞苷酸时，巨噬细胞细胞杀伤激活的另一个标志物NO2/NO3的合成会大幅减少。第三，β干扰素启动的巨噬细胞暴露于在触发过程中不诱导β干扰素产生的钙离子载体离子霉素或A23187时，与诱导β干扰素表达的刺激物（如聚肌胞苷酸）相比，Bf的表达缩短。然而，当巨噬细胞在持续存在β干扰素的情况下用离子载体触发时，对A23187反应合成Bf的能力部分得到恢复。总体而言，这些数据表明β干扰素在巨噬细胞细胞杀伤激活的触发阶段表达，并表明它在这种状态的表达中发挥了重要且此前未被怀疑的作用。
