Petering H, Götze O, Kimmig D, Smolarski R, Kapp A, Elsner J
Department of Dermatology and Allergology, Hannover Medical University, Hannover, Germany.
Blood. 1999 Jan 15;93(2):694-702.
Chemokines play an important role in attracting granulocytes into sites of inflammation. Two chemokine subfamilies differ in their biologic activity for different granulocyte subsets. Whereas CXC chemokines such as interleukin-8 (IL-8) activate predominantly neutrophils, CC chemokines such as RANTES and eotaxin activate predominantly eosinophils. However, controversial results have been published in the past regarding the biologic role of IL-8 in eosinophil activation, particularly in allergic diseases. In this study, we investigated the functional evidence and expression of both IL-8 receptors, CXCR1 and CXCR2, on highly purified human eosinophils. In the first set of experiments, a chemotaxis assay was performed showing that IL-8 did not induce chemotaxis of eosinophils. In addition, and in contrast to neutrophils and lymphocytes, IL-8 did not induce a rapid and transient release of cytosolic free Ca2+ ([Ca2+]i) in eosinophils, even after preincubation with TH1- and TH2-like cytokines. To investigate whether neutrophil contamination might be responsible for the reported IL-8 effects on eosinophils, neutrophils were added to highly purified eosinophils from the same donor in different concentrations. Interestingly, as little as 5% of neutrophil contamination was sufficient to induce an increase of [Ca2+]i after stimulation with IL-8. Flow cytometry experiments with monoclonal antibodies against both IL-8 receptors demonstrated no expression of CXCR1 and CXCR2 on eosinophils before or after cytokine activation. Reverse transcriptase-polymerase chain reaction experiments showed that eosinophils, in contrast to neutrophils and lymphocytes, did not express mRNA for CXCR1 and CXCR2. In summary, this study clearly demonstrates that CXCR1 and CXCR2 are not expressed on human eosinophils, even after priming with different bioactive cytokines. Because the CXC chemokine IL-8 did not induce in vitro effects on human eosinophils, IL-8 may also not contribute in vivo to the influx of eosinophil granulocytes into sites of allergic inflammation. Our results suggest that CC chemokines such as eotaxin, eotaxin-2, and MCP-4 are predominant for the activation of eosinophils.
趋化因子在吸引粒细胞进入炎症部位方面发挥着重要作用。两个趋化因子亚家族对不同粒细胞亚群的生物活性有所不同。诸如白细胞介素 - 8（IL - 8）等CXC趋化因子主要激活中性粒细胞，而诸如调节激活正常T细胞表达和分泌的因子（RANTES）和嗜酸性粒细胞趋化因子等CC趋化因子主要激活嗜酸性粒细胞。然而，过去关于IL - 8在嗜酸性粒细胞激活中的生物学作用，尤其是在过敏性疾病中的作用，已发表了一些有争议的结果。在本研究中，我们调查了IL - 8的两种受体CXCR1和CXCR2在高度纯化的人嗜酸性粒细胞上的功能证据及表达情况。在第一组实验中，进行了趋化性分析，结果显示IL - 8不会诱导嗜酸性粒细胞的趋化性。此外，与中性粒细胞和淋巴细胞不同，即使在用类似TH1和TH2的细胞因子预孵育后，IL - 8也不会在嗜酸性粒细胞中诱导细胞溶质游离钙（[Ca2 +]i）的快速短暂释放。为了研究是否是中性粒细胞污染导致了报道的IL - 8对嗜酸性粒细胞的影响，将不同浓度的中性粒细胞添加到来自同一供体的高度纯化的嗜酸性粒细胞中。有趣的是，低至5%的中性粒细胞污染就足以在IL - 8刺激后诱导[Ca2 +]i增加。用针对两种IL - 8受体的单克隆抗体进行的流式细胞术实验表明，在细胞因子激活前后，嗜酸性粒细胞上均未表达CXCR1和CXCR2。逆转录 - 聚合酶链反应实验表明，与中性粒细胞和淋巴细胞不同，嗜酸性粒细胞不表达CXCR1和CXCR2的mRNA。总之，本研究清楚地表明，即使在用不同的生物活性细胞因子启动后，人嗜酸性粒细胞上也不表达CXCR1和CXCR2。由于CXC趋化因子IL - 8在体外对人嗜酸性粒细胞没有诱导作用，IL - 8在体内可能也不会促使嗜酸性粒细胞流入过敏性炎症部位。我们的结果表明，诸如嗜酸性粒细胞趋化因子、嗜酸性粒细胞趋化因子 - 2和单核细胞趋化蛋白 - 4等CC趋化因子在嗜酸性粒细胞激活中起主要作用。
