Secretory IgA-, IgG- and C3b-coated Bacteria in the Nasopharynx of Otitis-Prone and Non-Otitis-Prone Children

Abstract

The proportions of secretory IgA (SIgA)-, IgG- and C3b-coated bacteria obtained from a well-defined area on the posterior wall of the nasopharynx (NPH) close to the Eustachian tube were determined. Samples taken from 25 otitis-prone (OP) and 25 non-otitis-prone (NOP) children with normal serum levels of IgA and IgG were evaluated using an immunofluorescence assay. Both groups harboured significantly more nasopharyngeal bacteria coated with IgG than with SIgA (p < 0.001). The OP children had significantly fewer SIgA-coated bacteria (p < 0.05) but more C3b-coated bacteria (p < 0.01) in the NPH than the NOP children had. No significant difference was noted between the two groups regarding IgG coating. The occurrence of Branhamella catarrhalis in the NHP was more pronounced in the OP group (p < 0.05). No significant differences in the occurrence of other middle ear pathogens (Streptococcus pneumoniae, Haemophilus influenzae, Staphylococcus aureus) or quantitative dominance of pathogens were noted between the two groups. Deficiency in SIgA coating of the nasopharyngeal bacteria may contribute to the otitis-prone condition.

Lower respiratory tract infection

“…Interestingly, otitis-prone children had significantly fewer secretory IgA-coated bacteria than did non-otitis-prone children. No significant difference was noted between the two groups regarding IgG coating (161). These two studies (59,161), which measured antibodies in the upper respiratory tract to homologous strains, suggest that the mucosal immune response is important in otitis media caused by B. catarrhalis.…”

“…No significant difference was noted between the two groups regarding IgG coating (161). These two studies (59,161), which measured antibodies in the upper respiratory tract to homologous strains, suggest that the mucosal immune response is important in otitis media caused by B. catarrhalis. The human immune response to B. catarrhalis, with particular emphasis on the mucosal immune response, is an area of investigation which should receive high priority.…”

“…Analysis of the systemic and local antibody responses to the homologous strains of B. catarrhalis following otitis media indicates that young children consistently develop a mucosal antibody response but fail to develop systemic antibody in a uniform manner (59). Children harbor B. catarrhalis which is coated with IgG and secretory IgA in the nasopharynx (161). Interestingly, otitis-prone children had significantly fewer secretory IgA-coated bacteria than did non-otitis-prone children.…”

“…Some studies have used a single strain (28,62,70,71), and some have used mixtures of strains (18,23,96,97,103,108). Other studies have used antigen preparations from homologous strains to study the immune response to the isolate infecting the patients (32,59,60,151,161). Different antigen preparations will yield markedly different results.…”

“…Several studies have established that antibodies to B. catarrhalis are present on the upper respiratory tract mucosal surface (59,96,97,161). Analysis of the systemic and local antibody responses to the homologous strains of B. catarrhalis following otitis media indicates that young children consistently develop a mucosal antibody response but fail to develop systemic antibody in a uniform manner (59).…”