Comparison of Chlamydia pneumoniae-specific T Effector Memory Lymphocytes in Asthmatic and Non-Asthmatic Adults

Chlamydia pneumoniae is a gram-negative intracellular bacterium that causes respiratory infections, and may contribute to inflammation in asthma. Studies in our laboratory demonstrated that T lymphocyte/cytokine responses to C. pneumoniae in children with asthma were significantly higher, compared with non-asthma, which may indicate the presence of T effector memory (TEM) lymphocytes. In the present study, C. pneumoniae -specific TEMs and their intracellular cytokines were compared in asthmatic and non-asthmatic adults.

Peripheral blood mononuclear cells (PBMC) (1×10⁶/mL) from asthmatic (N=6) and non-asthmatic (N=14) adults were infected for 24hr +/- C. pneumoniae TW-183 at a multiplicity of infection (MOI)=0.1 and cultured (48 hrs). Distributions of lymphocytes (CD3+, CD4+, CD8+) and TEM cells (CD4+CCR7-CD45RA+CD154+, CD8+CCR7-CD45RA+CD154+) were determined. Levels of intracellular Interleukin (IL)-2, IL-4, and Interferon (IFN)-gamma were measured (flow microfluorimetry).

Numbers of C. pneumoniae-stimulated CD3+CD4+CD45RO+CCR7-TEM (unstimulated, 1:10, 1:100) were higher in asthma compared with non-asthma (mean differences: unstimulated-stimulated) (-21±15, -17±15, -19±15; P=0.02, 0.04, 0.03, respectively) (Wilcoxon-signed rank test). However, CD3+CD4+IFN-gamma+TEMS (1:10, 1:100) were lower in asthma compared with non-asthma (mean differences: 2.2±5, 0.9±1; P=0.03, 0.04, respectively). When stratified according to C. pneumoniae IgG status, numbers of CD3+CD4+IL-2 (1:10) and CD3+CD4+IL-4+ (1:100) cells were higher in C. pneumoniae IgG+ compared with IgG- (mean differences: -0.2±0.2, -1.2±2.4; P=0.02. 0.05, respectively).

Increased numbers of C. pneumoniae -stimulated TEM cells in asthma may indicate decreased effectiveness in clearing infection, suggesting an impaired IFN-gamma response.