Immunologic aspects of otitis media with effusion. II. Nature of cell-mediated immunosuppressive activity in middle ear fluid.

The effects of middle ear effusions from patients with serous, seromucoid, mucoid, and purulent forms of otitis media with effusion on lymphoproliferative responses and polyclonal immunoglobulin synthesis were determined in peripheral blood and adenoidal lymphocytes. The responses were studied after stimulation of lymphocytes by phytohemagglutinin, pokeweed mitogen, purified protein derivative, herpes simplex virus, sheep red blood cells, or ovalbumin. Serous and seromucoid middle ear effusions resulted in significant suppression of proliferative responses to phytohemagglutinin, purified protein derivative, and herpes simplex virus and of polyclonal immunoglobulin synthesis in response to pokeweed mitogen, sheep red blood cells, and ovalbumin. The suppressive activity appeared to be associated with low-molecular-weight soluble products liberated by esterase-positive adherent population of cells in middle ear fluid.