Nasopharyngeal antibodies to pneumococcal capsular polysaccharides in children with acute otitis media.

Antibodies to pneumococcal capsular polysaccharides were measured by EIA in acute- and convalescent-phase nasopharyngeal aspirates from 120 children with acute otitis media. Nasopharyngeal IgM- and IgG-class antibodies were rare, whereas IgA was detected more often, occurred independently from serum IgA, and correlated with the presence of the secretory component in pneumococcal antibody, indicating local production of IgA. Thirty-four percent of the children with pneumococci in middle ear fluid developed a nasopharyngeal IgA response to the polysaccharide pool of serotypes 6B, 14, 19F, and 23F compared with 7% of the children with pneumococci only in the nasopharynx or not found at all (P = .004). The responses were observed in children of all ages, the youngest 6 months of age. This supports the hypothesis that mucosal immunity to bacterial polysaccharides matures earlier than systemic immunity.