Th1: mediator lymphocytes in experimental autoimmune labyrinthitis.

A previous study on experimental autoimmune labyrinthitis (EAL) consistently demonstrated transient infiltration of lymphocytes only into the inner ear of mice. To clarify the profile of lymphocytes in the initiation of EAL, the present study investigated cell surface antigens, as well as cytokines, from Day 4 to Day 35, using immunohistochemical techniques. Many CD4+ cells mainly infiltrated the endolymphatic sac as early as Day 4 and gradually spread to the rest of the inner ear. Infiltration peaked on Day 12 and persisted in most animals until Day 35, although the number of cells gradually decreased. In contrast, very few CD8+ cells were found to have appeared in the inner ear of all animals on Day 10, and the number of cells rapidly decreased. Many cells positive for IFN-gamma and IL-2 were identified in the endolymphatic sac on Day 4. These results suggest that helper T1 lymphocytes, rather than cytotoxic T lymphocytes, may play a central role in the initiation of EAL.