Chlamydia pneumoniae Induces Interferon Gamma Responses in Peripheral Blood Mononuclear Cells in Children with Allergic Asthma

Respiratory infections caused by Chlamydia pneumoniae have been associated with exacerbations of asthma. Cell‐mediated immunity ( CMI ) is critical for maintaining immunity. We compared interferon ( IFN )‐ γ responses in C. pneumoniae ‐infected peripheral blood mononuclear cells ( PBMC ) in paediatric patients ± asthma. Presence of C. pneumoniae was tested from asthma patients (N = 17) and non‐asthmatic controls ( N  = 16) ( PCR ). PBMC were infected for 1 h ± C. pneumoniae AR ‐39 ( MOI  = 0.1) and cultured for 48 h. IFN ‐ γ levels were measured in supernatants ( ELISA ). C. pneumoniae ‐IgG antibodies in serum were determined ( MIF ). All subjects tested negative for C. pneumoniae ( PCR ). C. pneumoniae ‐induced IFN ‐ γ production in vitro was more prevalent in asthma compared with non‐asthma; levels of IFN ‐ γ were higher in asthma compared with non‐asthma ( P  =   0.003). There was no association between recent respiratory infection and positive IFN ‐ γ responses. These data show that C. pneumoniae modulates IFN ‐ γ responses in patients with asthma, even in absence of active infection.