Characteristics of secretory immune system in human middle ear: implications in otitis media

The middle ear washings and biopsy specimens of middle ear mucosa from 20 patients with secretory otitis media were examined for the distribution of major classes of immunoglobulin; presence and nature of antibody activity against mumps, measles, rubella and poliovirus; and immunological localization of immunocompetent lymphoid cells. Appreciable amounts of secretory component, and γG, 7SγA, and 11S secretory γA immunoglobulin were regularly found in the ear fluids. The ratio of γG:γA immunoglobulin in the serum and middle ear fluids was approximately 10:1 and 10:4, respectively. Fluorescent antibody staining of mucosal tissues of middle ear demonstrated characteristic staining for secretory component in the surface epithelium, and the presence of γG and γA containing lymphoid tissue in the submucosa. Tissue culture studies demonstrated in vitro synthesis of γA and γG immunoglobulin and the secretory component in the mucosal tissues of middle ear. Specific antibody activity in the middle ear fluid against the viruses listed above was essentially limited to γA immunoglobulin, although such activity in the serum was predominantly associated with γG immunoglobulin. These data suggest the existence of a distinct secretory immune system in the middle ear. The implications of these observations may be applicable to the mechanism of protection, or pathogenesis of microbial infections in the middle ear.