Type B Haemophilus influenzae-induced otitis media in the mouse

To characterize the middle and inner ear cellular inflammatory responses to otitis media using immunohistochemical methods, we inoculated type B Haemophilus influenzae into the middle ears of healthy adult BALB/c mice. Mac-1+ neutrophils and macrophages appeared in the middle ear at 3 days. Lyt-1+ T cells and Lyt-2+ T suppressor/cytotoxic cells entered the middle ear mucosa on days 7 and 14. IgG+ and IgM+ T cells were present at all time points, with IgA+ lymphocytes forming the majority of mucosal immunoglobulin-bearing cells at 2 weeks. The cochlear scala tympani contained Lyt-1+ and Mac-1+ cells and two endolymphatic sacs stained diffusely with anti-IgA and -IgG antibodies. Lyt-1/L3T4+ T lymphocytes greatly outnumbered B lymphocytes, suggesting that helper/inducer T cells play a more important role in acute otitis media than has been recognized. Inner ear changes occurred after a single episode of otitis media.