MORPHOLOGICAL DIVERSITIES OF CD44 POSITIVE ASTROCYTES IN THE CEREBRAL-CORTEX OF NORMAL SUBJECTS AND PATIENTS WITH ALZHEIMERS-DISEASE

The localization of CD44 was investigated immunohistochemically in pos tmortem human brain tissue of control subjects and patients with Alzhe imer's disease. CD44 is a multifunctional cell surface glycoprotein th at serves as a receptor for hyaluronic acid, collagen types I and VI, and mucosal vascular addressin. In gray matter, it was found to be ass ociated with some astrocytes of both protoplasmic and fibrous morpholo gy. These positively stained astrocytes were most frequently observed in association with blood vessels, and had morphologies that were high ly comparable to those described with the Golgi technique. Double immu nostaining for CD44 and glial fibrillary acidic protein (GFAP) reveale d that a significant number of these astrocytes were positive for both antigens. However, GFAP staining was mostly confined to the cell soma ta and proximal processes, while CD44 staining extended to a rich and extensive array of processes. Occasional CD44 positive cells of spheri cal morphology with a few thin varicose processes were observed. Their processes formed thick terminations on blood vessels, suggesting that these cells are a special class of astrocyte. In Alzheimer's disease brain, the number of CD44 positive astrocytes increased dramatically. These data suggest that astrocytes have very extensive branching patte rns, which are reflected by CD44 staining patterns. CD44 may be an imp ortant adhesion molecule for these astrocytic processes.