Abstract: Abstract Objective To detect the mannosebinding lectin (MBL) serum levels and the mutation on code 54 of MBL in children with recurrent respiratory tract infections(RRTI),and to find the relationship between MBL serum levels and recurrent respiratory tract infections(RRTI).Methods To detect the serum MBL level of 238 normal people and 65 children with RRTI through the methods of enzymelinked immunoadsordent assay,then compare the immune data(IgG,IgA,IgM,C3,C4) of 11 children with low serum MBL level and compare the rate of the mutation on code 54 through the methods of polymerase chain reaction(PCR)restriction fragment length polymorphism (RFLP) with 55 normal children.Results The rate of low serum MBL level in the children with RRTI was higher than that in the normal population(χ²=6.96,P<0.05),the same went for the frequency of mutation of code 54 (P<0.05).RRTI caused by low serum MBL level occurred mostly among children under 2 years of age,and the rate of respiratory tract infection in the individuals with MBL level under 100μg/L was more than that in children with levels ranged from 100μg/L to 200μg/L (P<0.05),and was associated with reverse chang of serum levels of C3,C4(P<0.05).Conclusion Under 2 years of age,the children with the low serum MBL levels caused by mutation on MBL54 show the susceptivity to IRRTI,and the low serum MBL level is parallel to high serum levels of C3，C4，and the lower the level the more possible infection.

Key words: Polymorphism, Child , Repeated respiratory tract infections, Gene

摘要： 目的 了解反复呼吸道感染(RRTI)儿童血清甘露聚糖凝集素(MBL)水平及第一外显子54密码子的突变率，探讨血清MBL水平与RRTI的关系。方法 用ELISA方法检测2000~2003年在重庆医科大学附属儿童医院就诊的65例RRTI儿童和238名正常儿童血清MBL水平，测定其中11例低MBL血症的RRTI儿童的免疫学指标(IgG、IgA、IgM、C3、C4)，并用聚合酶链反应(PCR)限制性内切酶片段长度多态性分析(RFLP)方法与55名正常儿童MBL第一外显子54密码子基因多态性进行分析。结果RRTI儿童出现低血清MBL水平频率明显多于正常儿童(χ²=6.96,P<0.05)，其MBL54密码子突变率亦明显增高(P<0.05)，低血清MBL血症导致RRTI主要在2岁以前，血清MBL水平越低，感染频率越高，其C3、C4水平也越高。结论 儿童MBL54密码子突变导致低MBL血症在2岁以前有反复呼吸道感染的倾向，MBL水平越低，感染机率越高。

关键词: 甘露聚糖凝集素, 反复呼吸道感染, 基因, 多态性, 儿童