AN ASTROCYTIC BINDING-SITE FOR NEURONAL THY-1 AND ITS EFFECT ON NEURITE OUTGROWTH

Thy-1, a member of the immunoglobulin superfamily, is one of the most abundant glycoproteins on mammalian neurons. Nevertheless, its role in the peripheral or central nervous system is poorly understood. Certai n monoclonal antibodies to Thy-1 promote neurite outgrowth by rodent c entral nervous system neurons in vitro, suggesting that Thy-1 function s, in part, by modulating neurite outgrowth. We describe a binding sit e for Thy-1 on astrocytes. This Thy-1-binding protein has been charact erized by immunofluorescence with specific anti-idiotype monoclonal an tibodies and by three competitive binding assays using (i) anti-idioty pe antibodies, (ii) purified Thy-1, and (iii) Thy-1 transfected cells. The Thy-1-binding protein may participate in axonal or dendritic deve lopment in the nervous system.