Goodman R E, Nestle F, Naidu Y M, Green J M, Thompson C B, Nickoloff B J, Turka L A
Department of Medicine, University of Michigan, Ann Arbor 48109.
J Immunol. 1994 Jun 1;152(11):5189-98.
By using superantigens, we have found previously that keratinocytes activated by IFN-gamma could serve as accessory cells, providing costimulatory signals needed to induce T cell proliferation. Here, we compared the profile of cytokines produced by T cells stimulated in the presence of activated keratinocytes with the response seen using professional APCs. When keratinocytes are used as accessory cells there is a specific defect in T cell IFN-gamma production, whereas IL-2 and IL-4 are induced at levels comparable with those seen when professional APCs are used as accessory cells. Because keratinocytes express BB-1, a CD28-ligand distinct from B7-1 or B7-2 (which are found on professional APCs), we examined the possibility that the defect in IFN-gamma production might be a result of nonproductive CD28 engagement. However, even when the CD28 pathway is directly activated by a stimulatory mAb, there is no induction of IFN-gamma production in keratinocyte-supported cultures. In these same cultures IL-2 production is increased 10-fold, thus demonstrating a specific deficiency in the induction of IFN-gamma rather than a failure to respond to CD28 stimulation. Analysis by reverse transcriptase-PCR and ELISA for the inducible p40 chain of IL-12 reveals that keratinocytes produce little if any messenger RNA and no protein for IL-12 p40 compared with professional APCs. Addition of rIL-12 to keratinocyte-supported cultures restores IFN-gamma levels to those seen when professional APCs are present. Finally, when T cells are restimulated and analyzed at later time points (10 to 14 days) we find a refinement in cytokine profiles: T cells stimulated in the presence of professional APCs produced the Th1 cytokines IL-2 and IFN-gamma, whereas T cells stimulated in the presence of activated keratinocytes produced only the Th2 cytokine IL-4. The specific ability of keratinocytes to induce a Th2 response seems most closely linked to their absence of IL-12 production, and may be important in the maintenance of peripheral tolerance to self-Ags or in the immune response to exogenous Ags, pathogens, or haptens encountered in skin.
通过使用超抗原，我们先前发现，被γ干扰素激活的角质形成细胞可作为辅助细胞，提供诱导T细胞增殖所需的共刺激信号。在此，我们比较了在活化角质形成细胞存在的情况下刺激的T细胞产生的细胞因子谱与使用专职抗原呈递细胞（APC）时的反应。当角质形成细胞用作辅助细胞时，T细胞产生γ干扰素存在特定缺陷，而白细胞介素-2（IL-2）和白细胞介素-4（IL-4）的诱导水平与使用专职APC作为辅助细胞时相当。由于角质形成细胞表达BB-1，这是一种不同于B7-1或B7-2（存在于专职APC上）的CD28配体，我们研究了γ干扰素产生缺陷可能是无效CD28结合的结果的可能性。然而，即使CD28途径被刺激型单克隆抗体直接激活，在角质形成细胞支持的培养物中也不会诱导γ干扰素的产生。在这些相同的培养物中，IL-2的产生增加了10倍，从而证明了γ干扰素诱导存在特定缺陷，而不是对CD28刺激无反应。通过逆转录酶-聚合酶链反应（RT-PCR）和酶联免疫吸附测定（ELISA）分析IL-12的可诱导p40链发现，与专职APC相比，角质形成细胞产生的IL-12 p40信使核糖核酸（mRNA）极少甚至没有，也不产生蛋白质。向角质形成细胞支持的培养物中添加重组IL-12（rIL-12）可将γ干扰素水平恢复到存在专职APC时的水平。最后，当在稍后时间点（10至14天）对T细胞进行再刺激和分析时，我们发现细胞因子谱有所细化：在专职APC存在的情况下刺激的T细胞产生Th1细胞因子IL-2和γ干扰素，而在活化角质形成细胞存在的情况下刺激的T细胞仅产生Th2细胞因子IL-4。角质形成细胞诱导Th2反应的特定能力似乎与其不产生IL-12密切相关，这可能在外周对自身抗原的耐受维持或对皮肤中遇到的外源性抗原、病原体或半抗原的免疫反应中起重要作用。
