Serum cytokine levels, cigarette smoking and airway responsiveness among pregnant women

BACKGROUND

Five to twenty percent of healthy, nonasthmatic individuals exhibit airway hyperreactivity. Because cytokines are important intermediates in airway responses, we investigated the relationship between serum cytokines and airway responsiveness in a well-characterized population of pregnant women.

METHODS

We analyzed serum levels of interleukin-4 (IL-4), IL-5, IL-6, interferon-gamma (IFN-gamma), and granulocyte-macrophage colony-stimulating factor (GM-CSF) in frozen sera from 240 pregnant nonasthmatic subjects from a previous study of airway responsiveness and preterm labor for their relationship to methacholine challenge test results.

RESULTS

Serum IFN-gamma and GM-CSF levels were significantly related to levels of methacholine airway responsiveness among nonasthmatics in this population. Nonasthmatics with PD(20) <8 micromol (the highest level of airway responsiveness) had the highest mean serum levels of IFN-gamma and GM-CSF, those with 8 <or= PD(20) <or= >50 micromol had intermediate levels, and those with PD(20) >>50 mol had the lowest levels. Both serum IFN-gamma and GM-CSF levels were also significantly related to the log dose-response slope for methacholine responsiveness. These relationships were confirmed in a multiple linear regression analysis controlling for age, ethnic background, and cigarette smoking. Current smoking was uniformly associated with decreased cytokine levels.

CONCLUSION

IFN-gamma, GM-CSF, and other cytokines may be useful serum markers in population studies of airway responsiveness.