Selective inhibition of neurite outgrowth on mature astrocytes by Thy-1 glycoprotein.

THY-1, the smallest member of the immunoglobulin superfamily, is a major cell-surface component expressed by several tissues. The protein, carbohydrate and gene structures of this molecule are known, yet its function is not. It is highly expressed in nervous tissue, where it appears on virtually all neurons after the cessation of axonal growth. Here we show that expression of Thy-1 by a neural cell line inhibits neurite outgrowth on mature astrocytes, but not on other cellular substrata which include Schwann cells and embryonic glia. This inhibition of neurite extension on astrocytes can be reversed by low concentrations (nanomolar) of soluble Thy-1. If a similar interaction between neuronal Thy-1 and astrocytes occurs in vivo, it could stabilize neuronal connections and suppress axonal regrowth after injury in the astrocyte-rich areas of adult central nervous system.