Predominant Th2 type immune response in bronchoalveolar lavage fluid of patients with Mycoplasma pneumoniae pneumonia

Kim, Chang Keun; Chung, Churl Young

Abstract

OBJECTIVE
Mycoplasma pneumoniae infection is known as one of the frequent causes of exacerbation of bronchial asthma and it can also be a trigger for the initiation of asthma. However, little is known about the pathogenesis of respiratory M. pneumoniae infection. Furthermore, there is little data on human cytokine production and its involvement in the pathogenesis of M. pneumoniae infection. In order to investigate the immunopathogenesis of M. pneumoniae infection, we investigated the cytokine production in the bronchoalveolar lavage ( BAL ) fluid of patients with M. pneumoniae pneumonia and viral pneumonia, and compared the results with those of control subjects. SUBJECT AND METHOD: BAL was performed with fiberoptic bronchoscopy in patients with M. pneumoniae pneumonia( n=9 ), viral pneumonia( n=9 ), and control subjects( n=6 ) aged 3 years to 9 years. M. pneumoniae pneumonia was documented by polymerase chain reaction and serologic analysis. Four respiratory viruses ( adenovirus, influenza A, influenza B, parainfluenza ) were detected by culture method. Cell pellets and supernatants were separated by centrifugation and Interleukin( IL ) - 2, Interferon( IFN )-r, IL-4, and IL-5 levels were measured in concentrated BAL supernatants by ELISA.
RESULTS
Analysis of cytokines revealed significantly increased production of IL-4 ( p< 0.0001 ) and IL-2 ( p< 0.0001 ), in patients with M. pneumoniae pneumonia and significantly increased production of IL-2 (p <0.0001) in patients with viral pneumonia compared with those of the control subjects. Ratio of IL-4/IFN-r was significantly increased in patients with M. pneumoniae pneumonia ( p< 0.005 ) but not in patients with viral pneumonia compared with that of the control subjects.
CONCLUSION
IL-4 production and IL-4/IFN-r ratio were increased in the BAL fluid of patients with M. pneumoniae infection. These findings suggest that predominant Th2 immune response could play an important role in the pathogenesis of M. pneumoniae infection.