Immunofluorescent study on middle ear mucosa.

To clarify the developmental course of the immunological defense system in the middle ear, immunoglobulin-forming cells of different classes and secretory proteins, such as secretory component (SC) and lactoferrin (Lf), were investigated in the middle ear mucosa of 20 developing and 5 normal adult guinea pigs by use of direct immunofluorescence technique. Changes in the middle ear mucosa were also observed after antigenic challenges directly to the tympanic cavity of 6 developing and 39 adult guinea pigs. IgA- and IgM-forming cells began to appear in the tubal mucosa at the seventh postnatal day, while it was scarcely possible to find IgG1- and IgG2-forming cells in developing guinea pigs. Immunoglobulin-forming cells of all classes increased in the middle ear mucosa after the antigenic stimuli. The injection of antigens to the tympanic cavity of developing animals induced the most striking accumulation of immunoglobulin-forming cells in the middle ear mucosa. Results of this study showed that local synthesis of IgA, as well as other classes, is latent in the middle ear, that the middle ear of immature animals is vulnerable to antigenic stimuli, and that the middle ear of developing animals possesses potential immune responsiveness.