CD4⁺ T effector memory cell responses in Chlamydia pneumoniae-stimulated peripheral blood mononuclear cells in nonasthmatic subjects

Chlamydia pneumoniae (C. pneumoniae) is a gram-negative intracellular bacterium that causes respiratory infection in humans, including subjects with or without asthma. C. pneumoniae activates cells (e.g., monocytes/macrophages) in vitro, and produces cytokines that may contribute to inflammatory responses observed in asthma. Immunological differences exist between subjects with or without asthma, with regard to host responses to C. pneumoniae. The heterogeneity and subsequent diverse pathophysiology of asthma can be better understood by analyzing the repertoire of T-cell subpopulations; the most common distinction between different asthma endotypes includes cytokines produced by CD4⁺ cells (T helper (Th)2 high vs. Th2 low).