Inhibition of lymphoproliferation by middle ear effusion in experimental otitis media

In this study, experimental otitis media was created in the chinchilla by direct middle ear challenge with Escherichia coli endotoxin, Streptococcus pneumoniae, Haemophilus influenzae, or Pseudomonas aeruginosa. The effusions recovered from the chinchillas in all four challenge groups were shown to inhibit the lymphoproliferative response of chinchilla peripheral blood lymphocytes to stimulation with phytohemagglutinin. The effect was dose dependent, and for effusions of infectious origin, the degree of inhibition was directly related to the duration of infection. Presence of the inhibitor in plasma was undocumented, suggesting a local production within the middle ear. Lymphocytes from middle ears infected with bacteria but not middle ears challenged with endotoxin were hyporesponsive or nonresponsive to stimulation with phytohemagglutinin. These results confirm the presence of an inhibitor of the lymphoproliferative response in experimental otitis media of different etiologies.