目的　研究肺炎支原体肺炎患儿肺泡灌洗液(BALF)病菌量及其与Th1/Th2细胞免疫应答状况的相关性。方法　90例肺炎支原体肺炎患儿，以实时荧光定量PCR方法检测其BALF中肺炎支原体DNA(MP-DNA)含量，并分为低菌量组(≤106/ml)和高菌量组(>106/ml)，采用ELISA法检测并比较两组患儿BALF中白介素4(IL-4)、干扰素(IFN-γ)、IL-8和肿瘤坏死因子(TNF-α)，以及血清总IgE和ECP水平，以及MP-DNA拷贝数和炎症因子的相关性。结果　高菌量组BALF中IL-4水平和IL-4/IFN-γ明显高于低菌量组，差异有统计学意义(t=4.280、2.076，P均<0.05)；两组BALF中IFN、IL-8和TNF-α水平的差异无统计学意义(P>0.05)。高菌量组的血清总IgE和ECP阳性率均明显高于低菌量组，差异有统计学意义(χ2=24.638、6.392，P均<0.05)。患儿BALF中IL-4水平与MP-DNA拷贝数呈显著正相关(r=0.509，P<0.05)，IFN、IL-8及TNF-α与MP-DNA拷贝数则无相关性(P>0.05)。结论　肺炎支原体肺炎BALF中高菌量可诱导Th2免疫炎症因子产生，导致Th1/Th2免疫偏移，以Th2免疫反应占优势。

Objective　To understand the relationship between mycoplasm load in bronchoalveolar lavage fluid (BALF) with the status of Th1/Th2 immune response in children with Mycoplasma pneumoniae pneumonia (MPP). Methods　The levels of IL-4, IFN, IL-8 , TNF-α in BLAF and total IgE, ECP in serum from 90 children with MPP were measured by ELISA.MP DNA in BALF was detected quantitatively by fluorescent real-time PCR. Children with MPP (n=90) were divided into two groups of low MP-DNA load (n=24) and high MP-DNA load (n=26) according to the copies of MP DNA in BALF. The cytokines in BALF, and total IgE and ECP in serum were compared between the two groups. The relationship between the levels of cytokines in BLAF and the copies was evaluated. Results　The levels of IL-4 and the IL-4/IFN ratio in BALF from the high DNA-load group were significantly higher than that of the low group (t=4.280, 2.076, all P<0.05). The level of IL-4 was significantly correlated with the copies of MP-DNA in BALF from children with MPP (r=0.509, P<0.05). The percentage of total IgE and ECP positive result in serum from the high DNA-load group is higher than that of the low group. (χ2=24.638, 6.392, all P<0.05). Conclusion 　Infection with high-load MP in children may cause the imbalance of Th1/Th2. And the Th2 cytokines response seems predominant.