Snijders A, Hilkens C M, van der Pouw Kraan T C, Engel M, Aarden L A, Kapsenberg M L
Laboratory of Cell Biology and Histology, University of Amsterdam, The Netherlands.
J Immunol. 1996 Feb 1;156(3):1207-12.
IL-12 enhances IFN-gamma production by NK cells and T lymphocytes and plays a pivotal role in the development of Th1 cells. Bioactive IL-12 (p70) is composed of two subunits, p35, which is only secreted as part of the p70 dimer, and p40, which can also be secreted by itself. The IL-12 subunits are encoded by two separate genes. Therefore, we studied to what extent the expression of each of the subunits contributes to the regulation of IL-12 production. We found that in LPS-stimulated whole blood and purified monocytes, p70 and p40 production are enhanced by IFN-gamma and inhibited by IL-10 and IL-4. However, IFN-gamma and IL-10 had stronger effects on p70 production than on p40 production, and IL-4 affected p40 production more strongly. Concomitantly, in all experimental conditions tested, p40 production greatly exceeded p70 production, suggesting that p35 expression was limiting. Analysis of p35 and p40 mRNA expression by PCR confirmed this notion. Resting purified monocytes expressed neither p40 nor p35 mRNA. The effects of IFN-gamma, IL-10, and IL-4 on the p35 mRNA expression in LPS-stimulated purified monocytes were similar to the effects of these cytokines on p70 protein production, and the p40 mRNA expression corresponded to p40 protein production. Our results imply that production of the two IL-12 subunits is differently regulated for each subunit, mainly at the level of mRNA expression, and that the level of bioactive IL-12 production in monocytes in response to LPS and cytokines is determined by the level of p35 expression.
白细胞介素-12（IL-12）可增强自然杀伤细胞和T淋巴细胞产生γ干扰素（IFN-γ），并在Th1细胞的发育过程中起关键作用。具有生物活性的IL-12（p70）由两个亚基组成，即p35（仅作为p70二聚体的一部分分泌）和p40（也可自身分泌）。IL-12亚基由两个独立的基因编码。因此，我们研究了每个亚基的表达在多大程度上有助于调节IL-12的产生。我们发现，在脂多糖（LPS）刺激的全血和纯化单核细胞中，IFN-γ可增强p70和p40的产生，而IL-10和IL-4则抑制其产生。然而，IFN-γ和IL-10对p70产生的影响比对p40产生的影响更强，而IL-4对p40产生的影响更显著。同时，在所有测试的实验条件下，p40的产生大大超过p70的产生，这表明p35的表达是受限的。通过聚合酶链反应（PCR）分析p35和p40 mRNA的表达证实了这一观点。静息的纯化单核细胞既不表达p40 mRNA也不表达p35 mRNA。IFN-γ、IL-10和IL-4对LPS刺激的纯化单核细胞中p35 mRNA表达的影响与这些细胞因子对p70蛋白产生的影响相似，而p40 mRNA的表达与p40蛋白的产生相对应。我们的结果表明，两种IL-12亚基的产生对每个亚基的调节方式不同，主要在mRNA表达水平，并且单核细胞中响应LPS和细胞因子产生的生物活性IL-12的水平由p35的表达水平决定。
