Riemann H, Schwarz A, Grabbe S, Aragane Y, Luger T A, Wysocka M, Kubin M, Trinchieri G, Schwarz T
Department of Dermatology, University of Münster, Germany.
J Immunol. 1996 Mar 1;156(5):1799-803.
IL-12 is a heterodimeric cytokine with a powerful positive regulatory influence on the development of Th1 cell-mediated immune responses. Th1 cells are critically involved in contact hypersensitivity (CHS), so we were interested in studying whether IL-12 is of relevance in the induction phase of CHS. BALB/c mice were sensitized by epicutaneous application of 0.5% 2,4-dinitrofluorobenzene (DNFB) on the abdomen, draining lymph nodes obtained at various time points thereafter. RNA was extracted, and PCR analysis was performed using primers specific for the IL-12 subunits p35 and p40. Although p35 was constitutively expressed and not affected by hapten application, p40 transcripts were found to be enhanced in lymph nodes obtained between 12 and 24 h after sensitization. To study whether IL-12 is functionally relevant for the induction of CHS, an mAb directed against recombinant murine IL-12 was injected i.p. 3 and 24 h before sensitization. Challenge was performed 5 days later by painting the left ear with 0.3% DNFB. Whereas mice injected with sodium chloride or an isotype control Ab responded with a normal ear swelling after challenge with DNFB, mice treated with anti-IL-12 Ab showed a significantly reduced ear swelling response. To study whether injection of the IL-12 Ab causes transient nonresponsiveness or tolerance, resensitization was performed after a resting period of 14 days. Groups of mice initially treated with the anti-IL-12 Ab plus DNFB showed only a minimal response to DNFB after resensitization, suggesting that these mice became tolerant. Tolerance appeared to be hapten-specific because these mice could be successfully sensitized with the nonrelated hapten 2,4,6-trinitrochlorobenzene. Furthermore, when the anti-IL-12 Ab was injected into already sensitized mice before challenge, ear swelling response was significantly suppressed, suggesting that IL-12 also is involved in the effector phase of CHS. To exclude the possibility that the inhibitory effect of the anti-IL-12 Ab is simply due to an anti-inflammatory activity of the Ab, the anti-IL-12 Ab was injected i.p. 3 and 24 h before epicutaneous application of the toxic compound croton oil. However, irritant dermatitis elicited by croton oil was not affected by the Ab. Thus, the present study demonstrates that in vivo application of an anti-IL-12 Ab inhibits sensitization and induces hapten-specific tolerance and thus suggests that IL-12 may play a dominant in vivo role in the induction of CHS.
白细胞介素-12（IL-12）是一种异二聚体细胞因子，对Th1细胞介导的免疫反应的发展具有强大的正向调节作用。Th1细胞在接触性超敏反应（CHS）中起关键作用，因此我们有兴趣研究IL-12在CHS诱导阶段是否具有相关性。通过在BALB/c小鼠腹部经皮涂抹0.5% 2,4-二硝基氟苯（DNFB）使其致敏，此后在不同时间点获取引流淋巴结。提取RNA，并使用针对IL-12亚基p35和p40的特异性引物进行PCR分析。虽然p35组成性表达且不受半抗原涂抹的影响，但发现p40转录本在致敏后12至24小时获取的淋巴结中增强。为了研究IL-12在CHS诱导中是否具有功能相关性，在致敏前3小时和24小时腹腔注射针对重组鼠IL-12的单克隆抗体（mAb）。5天后通过用0.3% DNFB涂抹左耳进行激发。用氯化钠或同型对照抗体注射的小鼠在接受DNFB激发后耳部出现正常肿胀反应，而用抗IL-12抗体处理的小鼠耳部肿胀反应明显降低。为了研究注射IL-12抗体是否会导致短暂的无反应性或耐受性，在休息14天后进行再次致敏。最初用抗IL-12抗体加DNFB处理的小鼠组在再次致敏后对DNFB仅表现出最小反应，表明这些小鼠产生了耐受性。耐受性似乎是半抗原特异性的，因为这些小鼠可以用无关半抗原三硝基氯苯成功致敏。此外，当在激发前将抗IL-12抗体注射到已经致敏的小鼠中时，耳部肿胀反应明显受到抑制，表明IL-12也参与CHS的效应阶段。为了排除抗IL-12抗体的抑制作用仅仅是由于抗体的抗炎活性这一可能性，在经皮涂抹有毒化合物巴豆油前3小时和在24小时腹腔注射抗IL-12抗体。然而，巴豆油引起的刺激性皮炎不受该抗体影响。因此，本研究表明体内应用抗IL-12抗体可抑制致敏并诱导半抗原特异性耐受性，从而提示IL-12可能在体内CHS诱导中起主导作用。
