The development of mucosal immunity in guinea pig middle ears

Recent studies have suggested to us that the middle ear is an organ capable of responding immunologically to antigenic substance. However, it is still not known when and how the middle ear starts to provide the immunologic defense system. To clarify this, we investigated immunoglobulin forming cells of different classes and secretory proteins, such as secretory component and lactoferrin, in the mucous membrane of eustachian tube and tympanic bulla of 20 developing and 5 normal adult guinea pigs by the use of a direct immunofluorescence technique. Other organs, such as nose, larynx, trachea, small intestine, spleen and lymph node were also subjected to this investigation. 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 on 7th postnatal day, wile 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. 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.