Modulation of middle ear immune response by gut immunization.

Swallowing of upper respiratory pathogens which may at another time be involved in otitis media with effusion (OME) undoubtedly occurs in many patients. In order to explore the possible immunologic consequences to the middle ear (ME) of such gut exposure, guinea pigs were fed antigen either before or after systemic sensitization. A ME immune response was then elicited by ME antigenic challenge. Feeding before systemic sensitization induced systemic tolerance and blunted both the ME immune response and immune-mediated OME. Feeding after systemic sensitization amplified ME immunity and increased immune-mediated OME. Gut immunization, therefore, provides a potent modulation of ME immune response. Depending upon its timing, pathogen swallowing could produce immune hyporesponsiveness, with lowered resistance to infection but reduced immune-mediated inflammation. Alternatively, swallowing could result in immune hyperresponsiveness, with increased resistance but also increased inflammation.