Objective To observe the effect of dexamethasone on the levels of IL-12 and IL-13 in bronchoaveolar la-vage fluid (BALF) and serum in rats with Mycoplasma pneumoniae (MP) infection. To explore the mechanism of treatment MP pneumonia by dexamethasone. Methods A total of one hundred rats were randomly divided into four groups:azithromycin in-tervened group (n=25); dexamethasone intervened group (n=25); azithromycin and dexamethasone combination intervened group (n=25);control group (n=25). The rat model of MP pneumonia was established by dropping pneumonia bacterial liquid to its nasal cavity on day 0, 1, 2, and 3. Four groups received different interventions at the second day when the model was estab-lished successfully. Amounts of IL-12 and IL-13 in BALF and serum were measured by ELISA, the inflammatory infiltration of lung tissues was evaluated on day 3, 5 and 8. Results Compared with the control group, the expression of IL-12 and IL-13 in se-rum and BALF in azithromycin intervened group and combination intervened group had a significant difference (P<0.05) on day 3, 5 and 8. Amount of IL-12 in serum in combination intervened group was higher than azithromycin intervened group on day 3, whereas IL-13 was lower than that in azithromycin intervened group (P<0.05). Conclusions Dexamethasone can relieve inflammatory infiltration of lung tissues in rats.%目的：研究地塞米松对肺炎支原体（MP）感染大鼠血清及肺泡灌洗液（BALF）中IL-12、IL-13的影响，探讨其治疗MP肺炎的作用机制。方法100只SD大鼠随机分为4组：阿奇霉素组、地塞米松组、联合干预组和模型对照组，每组各25只。各组大鼠均予MP菌液（1×106 CFU/ml）缓慢滴入大鼠鼻腔，共4 d，在最后1次接种后第2天开始干预。采用ELI-SA方法监测干预后第3、5、8天大鼠血清及BALF液IL-12、IL-13水平，并对肺组织炎症浸润程度进行评分。结果在干预第3、5、8天，阿奇霉素组、地塞米松组、联合干预组及模型对照组肺组织病理评分比较差异均有统计学意义（F=8.71~20.11，P均<0.01），其中均以联合干预组评分最低。在干预第3、5、8天，四组间血清及BALF液中IL-12、IL-13水平比较差异均有统计学意义（F=9.52~143.47，P均<0.01）；其中干预第3天，联合干预组血清IL-12高于阿奇霉素组，而血清及BALF液IL-13均低于阿奇霉素组，差异均有统计学意义（P均<0.05）。结论地塞米松可能协同阿奇霉素通过促进大鼠体内IL-12分泌和抑制IL-13表达，减轻肺组织炎症。
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