Serum antipneumococcal antibodies and pneumococcal colonization in adults with chronic obstructive pulmonary disease.

Antibodies to pneumococcus are thought to represent the primary mechanism of naturally acquired resistance to colonization. Here, however, we show that, in patients with chronic obstructive pulmonary disease (COPD), resistance to pneumococcal colonization is not associated with higher concentrations of serum anti-capsular or -noncapsular antibodies. We compared preacquisition serum antibody concentrations to capsular antigens 6B, 7F, 14, 19F, and 23F from patients with COPD who did and did not acquire pneumococcal respiratory tree colonization over the course of 2 years. Colonized patients did not have lower anti-capsular antibody concentrations than control subjects who did not acquire pneumococcus. We found no difference in functional antibody concentrations between colonized patients and control subjects. Furthermore, colonized patients had significantly higher preacquisition concentration of antibody directed against the whole cell and pneumococcal surface protein A than control subjects. We thus conclude that, in adult patients with COPD, resistance to pneumococcal colonization is unlikely to be determined by higher serum antibody concentrations to pneumococcal antigens.