Immunoglobulins of the middle ear fluid in acute otitis media: relationship to serum immunoglobulin concentrations and bacterial cultures.

Immunoglobulin concentrations were studied in 255 specimens of middle ear fluid (MEF) from 165 episodes of acute otitis media in children. There were significant amounts of all three major immunoglobulins (Ig) in MEF, the mean concentration of IgA being 39 mg/100 ml, of IgM 63 mg/100 ml, and of IgG 383 mg/100 ml. Secretory component was present in all 10 MEF specimens in which it was sought. In patients over 9 months of age, there was a decreased likelihood of isolating pathogenic bacteria from MEF if the patient had higher concentrations of IgA in MEF than in simultaneously obtained serum. IgA concentrations were greater in MEF than in serum in almost half the patients, and the mean MEF-serum ratio for IgA was 1.38. Thus, it would appear that in this disorder MEF represents primarily a secretory response to inflammation rather than a transudate.