Neuronal cell Thy-1 glycoprotein: homology with immunoglobulin.

The amino acid sequences of mouse brain Thy-1 glycoproteins are shown to be homologous to those of variable-region immunoglobulin domains. There is also good homology with constant domains and beta 2-microglobulin; overall the results suggest that Thy-1 may be like the primordial immunoglobulin domain. Preliminary evidence for an invertebrate Thy-1 homolog supports this possibility.