目的：毛细支气管炎的确切发病机制尚不明确，常给治疗带来很大困难，目前认为毛细支气管炎是在病毒感染后继发的免疫功能异常。CD40/CD40L是免疫应答中的一对协同刺激分子，它们在毛细支气管炎的发病及IgE的产生中可能起到至关重要的作用。该文旨在观察毛细支气管炎患儿外周血单个核细胞（PBMC）CD40/CD40L的表达水平及其与血清IgE的相关性及与毛细支气管炎的发病关系。方法：采用流式细胞术对30例毛细支气管炎患儿，26例支气管肺炎患儿、30例正常对照组儿童PBMC CD40及CD40L的表达情况检测，同时用ELISA方法检测血清总IgE含量。结果：与对照组相比，CD40L在毛细支气管炎组和肺炎组表达均增高（P<0.05），且毛细支气管炎组的表达高于肺炎组（P<0.05）；CD40在毛细支气管炎组的表达高于肺炎组及对照组（P<0.01）；IgE在毛细支气管炎组的表达高于肺炎组和对照组（P<0.01），肺炎组和对照组差异无显著性意义；在毛细支气管炎组中CD40及CD40L的表达与IgE均成正相关（r＝0.607，0.819，均P<0.01），在肺炎组和对照组中二者无相关性。结论：毛细支气管炎患儿存在CD40/CD40L及IgE的表达增高，且二者具有正相关性，这可能是毛细支气管炎发生发展的重要机制。［中国当代儿科杂志，2009，11（5）：354-356］

OBJECTIVE: The pathogenesis of bronchiolitis has not been fully identified. Immune function abnormality following virus infection may be associated with the pathogenesis. CD40 and CD40 ligand (CD40L) is a pair of co-stimulatory molecules in immunoreaction. They might play an important role in the development of bronchiolitis. This study aimed to investigate the expression of CD40 and CD40L in peripheral blood mononuclear cells (PBMCs) in children with bronchiolitis and explore their possible roles in the disease. METHODS: Thirty children with bronchiolitis, 26 children with bronchopneumonia and 30 healthy children (control) were enrolled. Flow cytometry was used to detect CD40 and CD40L expression in PBMCs. Total serum IgE level was measured using ELISA. RESULTS: Compared with the control group, CD40L expression significantly increased in the bronchiolitis and bronchopneumonia groups (P<0.05). The CD40L expression in the bronchiolitis group was significantly higher than that in the bronchopneumonia group (P<0.05). A significantly increased CD40 expression was also found in the bronchiolitis group when compared with the bronchopneumonia and the control group (P<0.01). Total serum IgE level in the bronchiolitis group was significantly higher than the bronchopneumonia and the control groups (P<0.01). CD40 and CD40L expression was positively correlated with serum IgE level in the bronchiolitis group (r=0.607, r=0.819, respectively; P<0.01). CONCLUSIONS: CD40 and CD40L expression in PBMCs and serum IgE level increased and there is a positive correlation between CD40 and CD40L expression and serum IgE level in children with bronchiolitis. Over-expression of CD40 and CD40L may play an important role in the development of bronchiolitis.［Chin J Contemp Pediatr, 2009, 11 (5):354-356］