Expression of immunoregulatory cytokines during acute and chronic middle ear immune response

In both patients and experimental animals, immunoglobulin G (IgG) has been found to dominate acute otitis media with effusion (OME), whereas IgA tends to be present in chronic but not in acute OME. To determine whether local immunoregulation could account for this difference, the expression of cytokines associated with the production of different antibody isotypes was investigated in experimental acute and chronic OME. Mice were systemically immunized and then challenged transtympanically, once to produce an acute OME or once per week for 6 weeks to produce chronic OME. Hybridization with molecular probes for cytokine genes showed that cells producing interleukin-2 (IL-2) and IL-4, but not IL-5, were present during acute OME. In chronic OME, IL-2-positive (IL-2+) and IL-4+ cells were less prevalent, but IL-5+ cells were numerous. These finding support a model by which locally produced IL-2 and IL-4 augment IgG production in acute OME, whereas, IL-5 contributes to increased IgA production in chronic OME.