Comparison of Cytokine Responses (IL-21, IL-12, IL-13) in Chlamydia pneumoniae-Stimulated PBMC in Asthma and Non-Asthma

Objective. Chlamydia pneumoniae (C. pneumoniae) is a gram-negative intracellular bacterium that causes respiratory infections in humans. C. pneumoniae is responsible for cell activation and production of cytokines that may contribute to inflammatory responses in asthma. Cell-mediated immune responses are important for protective immunity; however, these responses may be impaired in asthma. In this study, we examined cytokine responses (IL-21, IL-12, IL-13) responsible for T helper (Th)1 versus Th2 responses in C. pneumoniae-stimulated PBMC from subjects with or without asthma. These cytokines could be potential biomarkers in the evaluation of past C. pneumoniae infection. Methods. Peripheral blood mononuclear cells (PBMC) (1×10⁶/mL) from stable adult asthmatic (N=6) and non-asthmatic subjects (N=6) were infected +/- C. pneumoniae TW-183 at a multiplicity of infection (MOI)=0.1, using dose responses (1:10, 1:100), and cultured 48 hrs. Cytokine responses (Interleukin (IL)-21, IL-12, IL-13) were measured in supernatants (ELISA). Results. Cytokine responses (mean differences: unstimulated-stimulated cells) were significant for IL-12 (1:10, 1:100) (P=0.0005, 0.0005) but not for IL-21 or IL-13 (Wilcoxon signed-rank test). Cytokine levels were higher in asthmatic subjects for IL-13 (mean differences: non-asthma-asthma) (unstimulated,1:10, 1:100) (-210±167, -140±113, -89±59, respectively) (P=0.05, 0.05, 0.05, respectively) compared with non-asthma. However, IL-21 and IL-12 responses were similar in both groups. When subjects were stratified according to C. pneumoniae IgG antibody status, no significant differences in cytokine responses were observed. Conclusion. Differential cytokine patterns in subjects with or without asthma may suggest a mechanism for the development of persistent infection with C. pneumoniae.