Expression of intercellular adhesion molecule-1 in immune response of inner ear

To understand the role of intercellular adhesion molecule-1 (ICAM-1) in immune response of the inner ear, inner ear immune response was induced in rats by inoculation of keyhole limpet hemocyanine (KLH) into the scala tympani of the animals who had been systemically sensitized. The expression of ICAM-1 in the inner ear was immunohistochemically examined. ICAM-1 was found in the epithelium of the spiral modiolar vein (SMV) with its collecting venules (CVs) as early as 6 h after challenge. Expression of ICAM-1 was observed on the epithelium of the endolymphatic sac (ES) and perisaccular region at 12 h. The intensity of ICAM-1 staining reached its peak within 24-48 h in these sites of the inner ear. By day 28, most specimens were devoid of appreciable staining for ICAM-1. Our study demonstrates that adhesion molecules play an important role in extravasation of inflammatory cells from the systemic circulation in the process of inner ear immune response. It also shows that cytokines that control expression of adhesion molecules may be released by cells outside ES, besides those cells in the ES.