Anatomic distribution and localization of immunocompetent cells in normal mouse endolymphatic sac

The distribution and anatomic localization of immunocompetent cells in normal mouse endolymphatic sac (ES) were examined by immunohistochemical methods. Antibodies against T cells (anti-Thy-1, -Lyt-1, -Lyt-2), macrophage (anti-Mac-1) and immunoglobulins (anti-IgM, -IgG, -IgA) were employed in an indirect technique utilizing strept-avidin-biotin complex. In the normal mouse ES, each of these cells could be detected by a difference in its frequency and distribution within and around the ES. Thy-1 positive (Thy-1+) cells are the most predominant in this tissue and can be seen throughout the ES. Lyt-1+ cells were found within the ES epithelium and in the perisaccular region, whereas Lyt-2+ cells were rarely present. Mac-1+ cells were present primarily in the lumen of the distal portion of the ES. IgM-bearing (IgM+) cells were seen in the subepithelial region, IgG+ cells were occasionally detected in the lumen and only a few IgA+ cells were present in the perisaccular region. This study revealed that the ES has the necessary immunological components for antigen processing and the generation of local immune responses within the inner ear.