Binding of peanut agglutinin is being widely used as a marker for immature mouse thymocytes and for the separation of these cells from the mature thymocytes. Two cell surface glycoproteins that bind peanut agglutinin were detected on unfractionated as well as immature thymocytes by lectin overlay and affinity chromatography: one of M r between 170000 and 180000, and the other, a minor component, of M r 110000, both of which are partially sialylated. No receptors for peanut agglutinin were detected on the mature cells, whereas desialylation experiments revealed the presence of a glycoprotein of M r 110000. These findings were corroborated by electrophoretic analysis of cell surface glycoproteins of the isolated thymocyte subpopulations labeled in their carbohydrate moieties.
