title: Chlamydia pneumoniae antibodies in chronic obstructive pulmonary disease.
abstract: BACKGROUND
  The significance of persistent or recurrent respiratory infections in adult life for the development of chronic obstructive pulmonary disease (COPD) is still to a large extent unknown. A few clinical and experimental animal studies suggest that peripheral airways diseases may be due to the cumulative effects of recurrent respiratory infections over an extended period.
  
  
  METHODS
  C. pneumoniae-specific IgG and IgA antibody levels were determined in two elderly groups of male patients with COPD and in control subjects without the disease. The first group (N = 36) consisted of patients who were hospitalized due to an acute exacerbation of COPD. The second group of patients (N = 54) and the controls (N = 321) were participants in a community survey on respiratory diseases in the elderly. The criteria for seropositivity were defined as an IgG titre of >=16.
  
  
  RESULTS
  89% of the hospitalized patients (group I) and 66% of the non-hospitalized patients (Group II) were IgA seropositive as compared to 55% of the controls. Derived from the logistic regression analysis, the odds ratio (OR) WAS 7.4 (95% CI : 2.1-25.7) between group I and the controls and 1.5 (0.7-2.9) between group II and controls. Furthermore, the difference in the age-adjusted geometric mean titres (GMT) of lgA antibodies between the group I and the controls was significant (53.0 for the patients versus 19.1 for the controls). On the contrary, no significant differences between the patients and the controls were found either in the proportion of IgG-seropositive or in the GMT of IgG antibodies. Two of the 29 patients with an exacerbation of COPD, for whom paired sera were available, showed an antibody response suggesting a current acute or reactivated chlamydial infection.
  
  
  CONCLUSIONS
  The results showed that C. pneumoniae lgA antibodies are found more frequently and in higher concentrations in COPD patients than in disease-free controls. The finding may indicate a chronic C. pneumoniae infection in these patients. The association persisted after controlling for the potential confounding effect of smoking.
authors.affiliation: Department of Respiratory Bacterial Infections, National Public Health Institute, FIN-00300 Helsinki, Finland.
authors.forename: L
authors.initials: L
authors.lastname: von Hertzen
authors.forename: R
authors.initials: R
authors.lastname: Isoaho
authors.forename: M
authors.initials: M
authors.lastname: Leinonen
authors.forename: R
authors.initials: R
authors.lastname: Koskinen
authors.forename: P
authors.initials: P
authors.lastname: Laippala
authors.forename: M
authors.initials: M
authors.lastname: Töyrylä
authors.forename: S L
authors.initials: SL
authors.lastname: Kivelä
authors.forename: P
authors.initials: P
authors.lastname: Saikku
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000907:Antibodies, Bacterial / Q000032:analysis*; D002690:Chlamydia Infections / Q000150:complications; D016993:Chlamydophila pneumoniae / Q000276:immunology*; D006801:Humans; D007070:Immunoglobulin A / Q000032:analysis; D007074:Immunoglobulin G / Q000032:analysis; D008173:Lung Diseases, Obstructive / Q000150:complications / Q000382:microbiology*; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio
chemical_list: D000907:Antibodies, Bacterial; D007070:Immunoglobulin A; D007074:Immunoglobulin G