CD8A and otitis media with effusion: Another study compared cell populations of CD4+ and CD8+ T cells, the CD4+/CD8+ ratio, the concentrations of the cytokines interleukin (IL)-2, IL-4, and IL-6, and the concentrations of immunoglobulin E (IgE) and nitric oxide (NO) in middle ear effusion (MEE) and the peripheral blood of 50 children with OME and 50 healthy children.