IL-13和乙醇促进人肺成纤维细胞胶原的表达

目的:研究乙醇和/或白细胞介素13(IL-13)对人肺成纤维细胞(HFL-1)Ⅰ、Ⅲ型胶原α1链基因(COL1A1、COL3A1)以及Ⅰ型胶原蛋白(CoⅠ)表达的影响,探讨肺纤维化的机制。方法:培养HFL-1,通过实时定量荧光RT-PCR检测乙醇和/或IL-13对HFL-1细胞IL-13受体(IL-13Rα1、IL-13Rα2、IL-4Rα)mRNA、COL1A1 mRNA和COL3A1 mRNA表达的影响,ELISA的方法检测乙醇和/或IL-13对HFL-1分泌CoⅠ的影响。结果:单独低浓度乙醇(25、50、100、200mmol/L)作用HFL-1后,与对照组相比IL-13Rα1 mRNA与IL-4Rα mRNA水平比对照组显著增高(P<0.05),而IL-13Rα2 mRNA水平比对照组显著降低(P<0.05)。单独低浓度乙醇(25、50、100、200 mmol/L)对HFL-1的COL1A1 mR-NA和COL3A1 mRNA表达无影响(P>0.05)。IL-13(10、20、50μg/L)可以促进HFL-1的COL1A1 mRNA和COL3A1 mR-NA的表达(P<0.05),且存在浓度依赖性。乙醇(200 mmol/L)与IL-13(10、20、50μg/L)共同作用刺激HFL-1促进COL1A1 mRNA和COL3A1 mRNA的表达比IL-13(10、20、50μg/L)单独作用强(P<0.05)。IL-13组(10、20、50μg/L)和乙醇(200 mmol/L)与IL-13(10、20、50μg/L)共同刺激组HFL-1均有CoⅠ的分泌,但共同刺激组HFL-1分泌CoⅠ量显著增加(P<0.05)。结论:单独低浓度乙醇(25、50、100、200mmol/L)不影响HFL-1细胞的COL1A1和COL3A1表达,但可以影响HFL-1细胞IL-4Rα、IL-13Rα1和IL-13Rα2的表达,而乙醇与IL-13共同刺激与单独IL-13刺激相比对HFL-1的COL1A1和COL3A1以及CoⅠ的表达有显著的促进作用。     

白三烯D_4和白介素13对人肺成纤维细胞白三烯受体1 mRNA表达及嗜酸粒细胞趋化因子产生的影响

探讨白三烯D4(LTD4)和白介素13(IL-13)对人肺成纤维细胞白三烯受体(CysLT1R)表达和eotaxin产生的影响。采用培养人肺成纤维细胞株(MRC-5),以不同浓度的IL-13进行刺激,用实时定量RT-PCR法测定CysLT1R mRNA表达的变化。再以不同浓度的LTD4和IL-13刺激,用ELISA法测定上清液中eotaxin的浓度,并观察Montelukast对eotaxin的产生是否有抑制作用。结果显示,培养的人肺成纤维细胞上存在着CysLT1R mRNA的低表达,以10 ng/ml IL-13刺激时,随着刺激时间延长,CysLT1R mRNA表达逐渐增高,48 h达高峰,较未刺激时表达增加(18.56±7.41)倍(P<0.01)。当以10 ng/ml和100 ng/ml的IL-13浓度刺激48 h时,较未刺激细胞CysLT1R mRNA表达分别增加(17.33±3.81)倍和(20.11±5.05)倍(P<0.01)。IL-13也能促进成纤维细胞产生eotaxin,以10 ng/ml和100 ng/ml的IL-13刺激成纤维细胞时,eotaxin浓度分别为(155.43±15.95)pg/ml和(221.31±17.23)pg/ml,较未刺激细胞(31.67±3.49)pg/ml明显增加(P<0.01)。单独给予LTD4刺激时,eotaxin浓度则无明显变化。但是以1×10-7mol/L和1×10-6mol/L浓度的LTD4分别联合10 ng/ml的IL-13共同刺激时,产生eotaxin的浓度分别为(204.4±25.4)pg/m和(255.1±38.3)pg/ml;较仅给予10 ng/ml的IL-13刺激时(155.4±16.0)pg/ml明显增加(P<0.01)。在LTD4+IL-13刺激组中,加入Mointelukast后eotaxin浓度为(148.3±15.7)pg/ml,较不加Montelukast(204.4±25.4)pg/ml明显降低(P<0.01)。人肺纤维细胞存在着CysLT1R mRNA的低表达,IL-13能够上调其表达,呈现时间与浓度依赖性。IL-13和LTD4对人肺成纤维细胞分泌的eoitaxin具有协同刺激作用,这可能与IL-13上调成纤维细胞CysLT1R mRNA表达有关,而Montelukast对这种刺激具有拮抗作用。     

JAK/STAT通路调节IL-4诱导的肝星状细胞I型胶原基因的表达

 目的：探讨JAK/STAT通路在IL-4对肝星状细胞(HSC)中I型胶原基因表达的影响及其作用机制。方法 用RT-PCR法和ELISA法分别检测不同浓度IL-4对人肝星状细胞系LX-2 中I型胶原mRNA表达和蛋白合成的影响;用Western blot法和RT-PCR法分别观察JAK1抑制剂AG490对IL-4诱导的JAK1磷酸化以及I型胶原mRNA表达的影响;用Western blot法和RT-PCR法分别观察LX-2转染STAT6-ASON对IL-4诱导的STAT6磷酸化以及I型胶原mRNA表达的影响。结果 IL-4诱导LX-2中I型胶原mRNA表达及其蛋白的合成,呈现剂量依赖性效应;AG490完全阻断IL-4诱导的JAK1磷酸化和I型胶原mRNA的表达;LX-2转染STAT6-ASON完全阻断IL-4诱导的STAT6磷酸化和I型胶原mRNA的表达。结论 JAK/STAT信号传导通路参与调节IL-4诱导HSC 中I型胶原基因表达,并在肝纤维化发生过程中发挥重要的作用。     

IL-4、IL-13蛋白表达及抗IL-4、IL-13人源单链抗体的筛选

目的:表达IL-4和IL-13蛋白,从人源单链抗体文库中分别筛选抗IL-4和抗IL-13单链抗体.方法:采用RT-PCR从健康志愿者外周血单核细胞(PBMC) mRNA中扩增IL-4和IL-13 cDNA;构建硫氧还蛋白融合表达载体,转化大肠杆菌BL21,IPTG诱导表达并对表达产物进行纯化鉴定.以生物素化的IL-4和IL-13为抗原从前期构建的人源抗体文库中采用噬菌体展示技术分别筛选抗IL-4和抗IL-13人源单链抗体(scFv).结果:扩增的IL-4 cDNA大小为280 bp,表达的融合蛋白大小为27 kD左右.扩增的IL-13 cDNA大小为252 bp,表达的融合蛋白大小为25 kD左右.分别以生物素化的IL-4和IL-13蛋白为抗原,采用噬菌体展示技术对人源抗体文库进行3轮富集后,分别有大约37％的scFvs与IL-4有结合特性,有约27％的scFvs与IL-13有结合特性.筛选了4株分别与IL-4和IL-13结合能力强的单链抗体进行了Westem blot鉴定和测序.结论:成功筛选到抗IL-4和抗IL-13人源性单链抗体.     

酪氨酸激酶抑制剂A771726阻断IL-13对成纤维细胞的促胶原合成作用

目的:观察酪氨酸激酶抑制剂A77 1726对白细胞介素13(IL-13)促成纤维细胞胶原合成作用的影响.方法:MTF法观察不同浓度的A77 1726对成纤维细胞的增殖作用的影响.成纤维细胞分为实验组和实验对照组,实验对照组加入IL-13(100 μg/L),实验组加入A77 1726(50 μmol/L)和IL-13(100μg/L),作用24、48、72 h后,羟脯氨酸(Hyp)检测A77 1726对IL-13促进成纤维细胞分泌胶原蛋白的影响,RTPCR观察A77 1726对IL-13促进成纤维细胞Ⅰ型胶原α1基因mRNA水平表达的影响,Western blot观察A77 1726对IL-13促进成纤维细胞分泌Ⅰ型胶原蛋白的影响.结果:A77 1726可抑制成纤维细胞的增殖.羟脯氨酸检测实验组48 h组和72 h组成纤维细胞分泌胶原蛋白的含量显著低于实验对照组(P＜0.05),RT-PCR观察到实验组48 h组和72 h组成纤维细胞Ⅰ型胶原α1基因(COLIA1)mRNA表达水平显著低于实验对照组(P＜0.05),Western blot观察到实验组48 h组和72 h组成纤维细胞分泌Ⅰ型胶原蛋白的水平显著低于空白对照组(P＜0.05).结论:酪氨酸酶抑制剂A77 1726阻断IL-13对成纤维细胞的促胶原蛋白合成作用,阻断IL-13促成纤维细胞Ⅰ型胶原α1基因mRNA水平和蛋白水平的表达.     

24例霍奇金淋巴瘤中IL-13Rα1的表达及意义

目的探讨白细胞介素13α1受体(IL-13Rα1)在霍奇金淋巴瘤(Hodgkin’s lymphoma,HL)中的表达及意义。方法采用免疫组化SP法检测IL-13Rα1在24例HL和15例间变性大细胞性淋巴瘤(anaplastic large cell lymphoma,ALCL)中的表达水平。结果 15例ALCL缺乏IL-13Rα1的表达,而24例HL中有20例(阳性率83.3%)存在IL-13Rα1的表达,两者差异有显著性(P<0.05)。结论 HL中存在IL-13Rα1的高表达,且IL-13Rα1检测可作为HL和ALCL鉴别诊断的依据。     

瘦素促进肺成纤维细胞向肌纤维母细胞的转分化

目的探讨瘦素对肺成纤维细胞向肌纤维母细胞转分化的影响及其作用机制。方法体外培养HFL-1人胚肺成纤维细胞,用(0~200)ng/m L重组人瘦素(r HL)干预或联合转化生长因子β1(TGF-β1)处理HFL-1细胞,Western blot法测定α平滑肌肌动蛋白(α-SMA)、蛋白激酶B(AKT)、磷酸化的AKT(p-AKT)的表达。CCK-8法测定细胞增殖,ELISA测定细胞上清液1型胶原蛋白含量。结果 (50、100、200)ng/m L的r HL处理HFL-1细胞48 h,α-SMA的蛋白表达水平均较对照组明显上调;与200 ng/m L r HL或5 ng/m L TGF-β1单独处理的细胞相比,200 ng/m L r HL和5 ng/m L TGF-β1联合处理HFL-1细胞48 h,HFL-1细胞α-SMA蛋白表达水平显著上调。r HL能够上调HFL-1细胞p-AKT的表达,LY294002可抑制r HL对HFL-1细胞α-SMA表达的诱导作用。与对照组相比,(12.5、25、50、100、200)ng/m L作用72 h,细胞存活率无显著性差异。(50~200)ng/m L r HL作用48 h,细胞上清液中1型胶原蛋白含量明显升高。结论瘦素能够促进肺成纤维细胞向肌纤维母细胞转分化,其作用机制与激活PI3K/AKT信号通路有关。     

白细胞介素13诱导Dami细胞分化并下调转录因子c-myc表达

目的：研究重组人白细胞介素13（recombinant human interleukine-13，rhIL-13）对巨核细胞白血病细胞株Dami细胞分化的影响，以及Dumi细胞白细胞介素13受体α1（Interleukine-13 receptor alpha 1，IL-13 Rα1）的表达，探讨IL-13诱导Dami细胞分化的机制。方法：Dumi细胞经无血清培养20小时后，以rhIL-13分别作用不同时间，提取总RNA，用RT—PCR检测Dumi细胞IL-13受体α1 mRNA、GPⅡb mRNA、c-myc mRNA表达水平。流式细胞仪检测在rhIL-13作用下，Dami细胞GPⅡb表达。免疫组化法检测在rhIL-13作用下，Dumi细胞c—myc的表达。图像分析仪对结果进行分析。结果：①Dami细胞表达IL-13 Rα1 mRNA，rhIL-13作用Dumi细胞4小时，IL-13 Rα1 mRNA表达降低，12小时IL-13 Rα1 mRNA表达恢复。②rhIL-13作用Dami细胞后，巨核细胞的分化标志物GPⅡb mRNA和蛋白质表达增加。③rhIL-13作用Dumi细胞，c—myc mRNA和蛋白质表达降低。结论：白细胞介素13下调c—myc表达。     

干扰素γ抑制IL-13对成纤维细胞的纤维化作用

 目的：研究干扰素γ（IFN-γ）抑制白细胞介素13（IL-13）对成纤维细胞纤维化作用的影响。方法：将成纤维细胞分为实验组和空白对照组,实验组加入IFN-γ（4×105 U/L）和IL-13（100 μg/L）,共同作用24、48和72 h后,分别用羟脯氨酸法、RT-PCR和Western blotting检测成纤维细胞分泌胶原蛋白、I型胶原α1(Col 1A1)mRNA表达和I型胶原蛋白的表达水平。另外对比空白对照组、IFN-γ组、IL-13组和IFN-γ+IL-13组72 h后Col1A1 mRNA表达和I型胶原蛋白的表达水平。结果：MTT结果表明IFN-γ浓度增加到4×105 U/L后可显著抑制成纤维细胞的增殖（P<0.01）。羟脯氨酸法检测显示48 h和72 h实验组成纤维细胞分泌的胶原蛋白含量显著低于空白对照组（P<0.05）;RT-PCR分析结果揭示48 h和72 h实验组的Col1A1 mRNA表达水平显著低于空白对照组（P<0.05）;Western blotting检测也进一步证实了48 h和72 h实验组成纤维细胞分泌I型胶原蛋白的水平显著低于空白对照组。另外各因素组对比结果显示, 72 h后IFN-γ组Col1A1 mRNA和蛋白的表达水平显著低于空白对照组（P<0.05）,IL-13组显著高于空白对照组（P<0.05）,而IFN-γ+IL-13组显著低于显著低于其它组（P<0.01）。结论：IFN-γ可抑制IL-13对成纤维细胞的纤维化作用。     

IL-4 and IL-13 Induce Chemotaxis of Human Foreskin Fibroblasts, But Not Human Fetal Lung Fibroblasts

Through shared receptors, IL-4 and IL-13 have been suggested to regulate not only inflammatory cells, but also to play a role in stimulating fibroblasts during fibrotic processes. Previous studies have shown that IL-4 is a chemoattractant for foreskin fibroblasts. The current study was designed to determine the effect of IL-4 and IL-13 on the migration of two types of fibroblasts: foreskin and human fetal lung fibroblasts (HFL-1). Using the Boyden blindwell chamber method, human foreskin or fetal lung fibroblasts (both 10(6)/mL) were placed in upper wells with various concentrations of IL-4 or IL-13 in the lower wells as chemoattractants. Both IL-4 (1 pg/mL) and IL-13 (100 pg/mL) induced foreskin fibroblast chemotaxis, up to 50 +/- 8 and 24 +/- 7 cells/5 high-power fields, respectively (both p < 0.05). In contrast, neither cytokine induced migration of the lung fibroblasts although both type of cells express IL-4 receptor and IL-13alpha1 receptor. These results suggest that fibroblasts are heterogeneous with regard to their ability to respond to cytokine-driven chemotaxis. Therefore, the role of specific cytokines in mediating fibrotic responses might vary depending on local mesenchymal cell responses.     

Therapeutic targeting of IL-4-and IL-13-responsive cells in pulmonary fibrosis

Severe forms of idiopathic interstitial pneumonia (IIP), such as usual interstitial pneumonia (UIP), can be impervious to modern steroid and immunosuppressive treatment regimens, thereby emphasizing the need for novel effective therapies. Understanding the cytokine networks that may affect immune and structural cell activation and, hence, the progression of these fatal fibrotic diseases, has been a focus in our research. In this regard, we have examined the role of interleukin (IL)-4 and IL-13 and their respective receptor subunits in this process. Examination of clinical surgical lung biopsies (SLBs) showed that IIP is characterized by the abnormal, heightened expression of the receptor subunits that bind IL-4 and IL-13. Specifically, IL-4Rα and IL-13Rα2 (the high-affinity IL-13 receptor subunit) was present in greater abundance in SLBs and fibroblasts from IIP patients compared with normal patients, who exhibited no evidence of pulmonary fibrosis. These clinical findings prompted us to investigate whether the targeting of pulmonary cell types that were highly responsive to IL-4 and IL-13 was a viable therapeutic option in IIP. Using a chimeric protein comprised of human IL-13 and a truncated version of an exotoxin from Pseudomonas (abbreviated IL13-PE), we observed that IL13-PE selectively targeted human pulmonary fibroblasts grown from IIP SLBs, whereas it had a minimal effect on fibroblasts grown from biopsies from normal patients. In murine models characterized by abnormal airway or interstitial fibrotic responses, the intranasal administration of IL13-PE significantly attenuated the fibrotic response through the targeting of IL-4Rα-and IL-13Rα2-expressing pulmonary cells, including monocytes, macrophages, and pulmonary fibroblasts. Together, these data demonstrate that IL-4 and IL-13 are required for the initiation and maintenance of pulmonary fibrosis, and highlight the importance of further investigation of anti-fibrotic therapeutics that prevent the action of both cytokines during clinical pulmonary fibrosis.     

Interleukin-13 acts as an apoptotic effector on lung epithelial cells and induces pro-fibrotic gene expression in lung fibroblasts

Background IL‐13 promotes acute allergic asthma and is discussed to play a role in late asthmatic features such as fibrotic processes and airway remodelling. The contributions of IL‐13‐mediated mechanisms to subepithelial events related to fibrosis are not yet settled. Objective We investigated the impact of IL‐13 on lung epithelial cells as apoptotic effector and on lung fibroblasts as inducer of pro‐fibrotic gene expression. Methods Using the two lung epithelial cell lines A549 and BEAS‐2B as well as primary lung epithelial cells, we investigated the capability of IL‐13 to induce apoptosis by both flow‐cytometry and ELISA. The ability of IL‐13 to increase the expression of pro‐fibrotic genes and to exert influence on the expression of its own receptor was investigated by real‐time quantitative PCR measurement of mRNAs encoding collagen I, collagen III, basic fibroblast growth factor (bFGF), α‐smooth muscle actin (α‐SMA) and the IL‐13 receptor α1 (IL‐13Rα1) chain in human primary lung fibroblasts. The specificity of IL‐13‐mediated cellular responses was confirmed by means of an inhibitory monoclonal antibody directed to the IL‐13 receptor. Results IL‐13 induces apoptosis in lung epithelial cell lines as well as in primary lung epithelial cells. Furthermore, IL‐13 increases the expression of mRNA for α‐SMA and collagen III, but not for bFGF in human primary lung fibroblasts. The susceptibility of lung fibroblasts to IL‐13‐induced up‐regulation of pro‐fibrotic genes is associated with the regulation of IL‐13 receptor expression. IL‐13‐dependent fibrosis‐associated effects could be inhibited by antibody‐mediated blockade of the IL‐13Rα1 subunit. Conclusion Our findings indicate a function of IL‐13 as a mediator in fibrotic processes leading to loss of functional airway tissue in asthma. They also highlight the therapeutic potential of specifically targeting the interaction between IL‐13 and its receptor.     

IL-13Ralpha2 reverses the effects of IL-13 and IL-4 on bronchial reactivity and acetylcholine-induced Ca+ signaling

BACKGROUND: The interleukins IL-4 and IL-13 play a key role in the pathophysiology of asthma. The interleukin receptor IL-13Ralpha2 is believed to act as a decoy receptor, but until now, the functional significance of IL-13Ralpha2 remains vague. METHODS: Bronchial reactivity was quantified in murine lung slices by digital video microscopy and acetylcholine (ACH)-induced Ca(2+) signaling was measured in human airway smooth muscle cells (ASMC) using fluorescence microscopy. RESULTS: IL-4 or IL-13 up to 50 ng/ml induced bronchial hyperreactivity. But after incubation with 100 ng/ml this effect was lost and bronchial responsiveness was again comparable to the control level. The effects of IL-4 and IL-13 on bronchial reactivity were paralleled by the effects on ASMC proliferation. Fifty nanograms per milliliter of IL-4 and IL-13 increased the Ca(2+) response of human ASMC to ACH. At 100 ng/ml, however, the effects of the cytokines on the Ca(2+) response were no longer evident. The expression of IL-13Ralpha2 increased with increasing concentrations of IL-4 or IL-13, reaching its maximum at 100 ng/ml. Blocking IL-13Ralpha2, the loss of the effect of IL-4 and IL-13 at 100 ng/ml on human ASMC proliferation and the ACH-induced Ca(2+) response were no longer present. CONCLUSIONS: IL-4 and IL-13 induce bronchial hyperreactivity by changing the Ca(2+) homeostasis of ASMC. These effects are counteracted by IL-13Ralpha2. The biological significance of IL-13Ralpha2 might be a protective function by regulating IL-13- and IL-4-mediated signal transduction and thereby limiting pathological alterations in Th2-mediated inflammatory diseases.     

IL-13 R110Q,a Naturally Occurring IL-13 Polymorphism,Confers Enhanced Functional Activity in Cultured Human Bronchial Smooth Muscle Cells

Purpose

Interleukin (IL)-13, a Th2-type cytokine, plays a pivotal role in the pathogenesis of asthma through its direct effects on airway smooth muscles. A naturally occurring IL-13 polymorphism, R110Q, is strongly associated with increased total serum IgE levels and asthma. In the present study, we aimed to determine whether the IL-13 R110Q variant would display different biochemical properties or altered functions in comparison with wild-type (WT) IL-13 in cultured human bronchial smooth muscle cells (hBSMCs).

Methods

Culture supernatants and cell proteins were collected from cultured hBSMCs that were treated with 50 ng/mL IL-13 or IL-13 R110Q for 24 hours. Eotaxin released into hBSMC culture medium was determined by ELISA. The expression levels of the high-affinity IgE receptor (FcεRI) α-chain, smooth muscle-specific actin alpha chain (α-SMA), smooth muscle myosin heavy chain (SmMHC), and calreticulin in the cells were measured on Western blots.

Results

Compared with WT IL-13, treatment with the IL-13 R110Q variant resulted in a significant increase in eotaxin release as well as significant, although modest, increases in the expression levels of α-SMA, SmMHC, calreticulin, and FcεRI α-chain.

Conclusions

The results of the present study suggenst that the IL-13 R110Q variant may enhance enhanced functional activities in hBSMCs.     

Tumor cells secreting IL-13 but not IL-13Ralpha2 fusion protein have reduced tumorigenicity in vivo

IL-13 is a Th2 cytokine that plays crucial roles in the pathophysiology of allergy, asthma and helminth infection. The high affinity receptor for IL-13, IL-13Ralpha2, may act as a decoy receptor for IL-13. The anti-tumor effect of IL-13 and its soluble receptor IL-13Ralpha2 have been examined in different tumor systems. Previous studies have shown that IL-13 enhances anti-tumor responses in some model systems, whereas IL-13Ralpha2Fc prevents IL-13 mediated suppression of tumor immuno-surveillance in a different model system. In this study, we have used a cytokine (receptor) gene therapy approach and studied the immune responses mediated by IL-13 and IL-13Ralpha2Fc in poorly immunogenic B16F1 melanoma and immunogenic MethA fibrosarcoma tumor models. We find that IL-13 reduces the tumorigenicity of B16F1 melanoma and MethA fibrosarcoma cells in vivo, most likely through the recruitment of neutrophils and macrophages. IL-13 mediated anti-tumor responses do not lead to the generation of tumor-specific T cells. Neither IL-13Ralpha2Fc gene transduction nor in vivo treatment with soluble IL-13Ralpha2Fc has a statistically significant effect of tumor growth. IL-13Ralpha2 deficient host background does not alter tumor growth, suggesting that endogenous levels of IL-13 do not contribute to an anti-tumor response in these models. We conclude that IL-13, but not soluble IL-13Ralpha2, has anti-tumor activity in the models described here, possibly by enhancing innate anti-tumor immunity.     

Mast cells express IL-13R alpha 1: IL-13 promotes human lung mast cell proliferation and Fc epsilon RI expression

BACKGROUND: The Th2 cytokine interleukin (IL)-13 is implicated in the development of various allergic diseases including asthma. The IL-13 receptor, IL-13Ralpha1, is expressed on most leukocytes, except T-cells. Evidence to support IL-13Ralpha1 expression on mast cells is limited. METHODS: We investigated: (i) IL-13Ralpha1 expression by human lung mast cells (HLMC); (ii) the number of IL-13Ralpha1+ bronchial submucosal mast cells in subjects with asthma and normal controls and (iii) the effect of IL-13 priming on HLMC expression of high-affinity IgE receptor (FcepsilonRI), stem cell factor receptor (CD117), histamine release, proliferation, and survival. RESULTS: Human lung mast cell expressed IL-13Ralpha1 mRNA. IL-13Ralpha1 was highly expressed on the surface HLMC (82+/-9%). Bronchial submucosal mast cell IL-13Ralpha1 expression was higher in asthmatics (86+/-2%) than normal controls (78+/-2%; P=0.015). IL-13 priming for 30 min did not increase HLMC histamine release, in the presence or absence of SCF or in response to IgE/anti-IgE activation. IL-13 priming for 5 days upregulated HLMC FcepsilonRI expression (22% increase in fluorescent intensity; P=0.003), increased histamine release following IgE/anti-IgE activation by 56% (P=0.03) and increased proliferation by 50% (P=0.003) without affecting cell survival or CD117 expression. The IL-13 specific neutralizing antibody CAT-354 inhibited all IL-13 mediated effects. CONCLUSION: Human lung mast cell express IL-13Ralpha1 and activation by IL-13 for 5 days increased FcepsilonRI expression and proliferation. Histamine release was not affected by short-term priming with IL-13, but was upregulated by priming for 5 days suggesting that this effect was mediated by the increased FcepsilonRI expression. These data support the view that targeting IL-13 may be beneficial in the treatment of asthma.