Immunological potential of the tympanic membrane. Observation under normal and inflammatory conditions

Purpose: The immunological potential of the murine tympanic membrane was studied under normal and inflammatory conditions. Materials and Methods: Experimental otitis media was induced by injecting keyhole limpet hemocyanin into the tympanic cavity of systemically sensitized mice. The animals were killed from 1 day to 2 weeks after the injection, and the distribution of the immunocompetent cells in the tympanic membrane was compared with those in normal animals, by immunohistochemical and toluidine blue staining. Results: Tympanic membranes under normal conditions showed few immunocompetent cells, except mast cells and la-positive dendritic cells (presumably Langerhans' cells) in the pars flaccida and in the annular and manubrial regions of the pars tensa. After the induction of otitis media, lymphocytes migrated into these regions, although the other regions of the pars tensa showed few of these cells. la-positive cells migrated into both pars tensa and pars flaccida. Mast cells did not show obvious changes between the normal and inflammatory conditions. Conclusion: The pars flaccida and the annular and manubrial regions of the pars tensa are considered to be the immunologically potential sites, responsible for the immune responses. The remaining greater part of the tympanic membrane can recognize antigens by the migrated Langerhans' cells. Copyright (C) 1997 by W.B. Saunders Company.