MACROPHAGES AND ENDOTHELIAL-CELLS EXPRESS INTERCELLULAR-ADHESION MOLECULE-1 IN IMMUNE-MEDIATED DEMYELINATION BUT NOT IN WALLERIAN DEGENERATION OF THE RAT PERIPHERAL NERVOUS-SYSTEM

BACKGROUND: Intercellular adhesion molecule-1 (ICAM-1) plays an import ant role in immune responses, especially in T cell/endothelial cell an d T cell/macrophage interactions. This study reports the cellular loca lization of ICAM-1 during immune-mediated demyelination of the periphe ral nervous system induced by adoptive transfer of P2 specific T cells . EXPERIMENTAL DESIGN: Cryosections 1 mum thick of ventral roots of ra ts with experimental autoimmune neuritis were labeled with a monoclona l antibody against rat ICAM- 1. RESULTS: Numerous ICAM-1 positive cell s were present before and shortly after the onset of clinical disease from days 4 to 6 after cell transfer. By day 8, their number had great ly decreased. ICAM-1 positive infiltrating cells could be identified a s ED1 positive macrophages. Moreover, endothelial cells expressed ICAM -1. Schwann cells and T cells were ICAM-1 negative. While at early sta ges of experimental autoimmune neuritis, ICAM-1 and la colocalized on macrophages but not endothelial cells, la persisted for a longer perio d in nerve roots than ICAM-1. After nerve transection, macrophages ent ering the distal stump and endothelial cells did not express ICAM- 1. CONCLUSIONS: The presence of ICAM-1 immunoreactivity in peripheral ner ve indicates an underlying immune-mediated process. Among other cytoki nes interferon-gamma, which is transiently expressed in nerves during immune-mediated demyelination but not after nerve transection, could b e one mediator that induces ICAM-1 in immune-mediated demyelination of the peripheral nervous system.