Chlamydia pneumoniae-Immunoglobulin E antibody responses in serum from children with asthma.

Chlamydia pneumoniae is an obligate intracellular bacterium that causes respiratory infection in humans. An association between persistent C. pneumoniae infection and asthma pathogenesis has been described. It is unknown whether specific IgE is a marker of persistent immune activation responses. Therefore, the association between C. pneumoniae specific IgE antibodies (Abs) and interferon (IFN)-gamma produced by C. pneumoniae-stimulated PBMC was examined. Blood was collected and serum separated. Peripheral blood mononuclear cells (PBMC) from 63 children with or without stable asthma (N = 45 and 18, respectively) were infected or not infected with C. pneumoniae AR-39 and cultured up to 7 days. Supernatants were collected, and IFN-gamma levels measured (ELISA). Serum C. pneumoniae- IgE Abs were detected by immunoblotting. C. pneumoniae IgE Abs were detected in asthmatics (27%), compared with non-asthmatics (11%) (P = NS). IFN-gamma responses were more prevalent among asthmatics who had positive C. pneumoniae-IgE Abs (91%) compared with asthmatics without C. pneumoniae-IgE Abs (20%) (P = 0.0046). IFN-gamma responses in C. pneumoniae stimulated PBMC from children with asthma were significantly more frequent in children who had specific anti-C. pneumoniae IgE Abs compared to those who did not. This immune response may reflect persistent infection which may contribute to ongoing asthma symptoms.