Expression of Intercellular Adhesion Molecule 1 (ICAM-1) in Alzheimer's Disease

In this study, 13 clinically and pathologically diagnosed cases of Alzheimer's disease were analyzed for the presence of intercellular adhesion molecule 1 (ICAM-1), ICAM-2, lymphocyte function associated antigen-1 (LFA-1), HLA-DR, LN-1, and LN-2. ICAM-1 was observed primarily on neuritic plaques and cerebrovascular endothelium. ICAM-1 was also shown to be present in brain tissue derived from 14 normal cases; however, the degree of immunoreactivity was quantitatively less compared to Alzheimer cases and was largely restricted to cerebrovascular endothelium. LFA-1 was shown to be present on microglial cells and leukocytes. Consistent with the findings of previous reports, HLA-DR was found to be expressed on microglial cells. In this study we failed to demonstrate dual immunolocalization for ICAM-1 and LFA-1, ICAM-1 and HLA-DR, or ICAM-1 and LN-2. As microglial cells express both HLA-DR and LFA-1, they may serve to mediate antigen presentation functions by interacting with lymphocyte ICAM-1. Alternately, the expression of these immune-associated glycoproteins on glial cells may be epiphenomenal occurring secondary to some aspect of the disease process. Finally, the presence of ICAM-1 within neuritic plaques raises the question as to whether adhesion may play some role in the process of neurite outgrowth and neurodegeneration.