New perspectives on immunologic reactivity in otitis media with effusion

It has been well established that the normal middle ear mucosa (MEM) when ventilated by a normal eustachian tube is essentially devoid of immunologic elements such as lymphocytes, plasma cells, and macrophages. Furthermore, neutrophils are rarely, if ever, found in the normal MEM. Thus, the development of an immune response in otitis media must occur following a series of events that are physiologically and bacteriologically abnormal. The great bulk of evidence would support the concept that eustachian tube dysfunction, or blockage, is preeminent in the development of negative pressure in the middle ear. Following the development of negative pressure, an effusion occurs in the middle ear space. This fluid is usually of a serous nature, and it has been demonstrated that mucoid effusion does not occur in the germ-free animal, nor does the development of an increased number of goblet cells and glands occur in the germ-free animal. Therefore, it appears that at least in acute otitis media and most forms of otitis media with effusion (OME), bacteriologic factors are necessary for the influx of immunocompetent cells. One of the questions that has not been answered at the present time is the source of the immunocompetent cells that reach the middle ear in acute and chronic OME. Three definite possibilities exist in this regard: 1) the gastrointestinal-associated lymphoid tissue (GALT), 2) the bronchus-associated lymphoid tissue (BALT), and 3) the tonsils and adenoids.