The carbohydrate component of Glycoprotein 2 (12% carbohydrate) from rye-grass (Lolium perenne) pollen has saccharide sequences that contribute to its antigenicity. Radioimmunoassay inhibition tests show that the antiserum to this glycoprotein cross-reacts with a number of other plant glycoproteins. In contrast, antiserum to another glycoprotein from rye-grass pollen, Glycoprotein 1 (5% carbohydrate), does not cross-react with any of the test glycoconjugates. Treatment of glycoproteins with sodium metaperiodate (0.02 M, 4 degree C, 6 h, in the dark) causes the loss of their ability to cross-react antigenically with Glycoprotein 2, and a loss of capacity to bind 125I-labelled concanavalin A. The cross-reactivity of this plant glycoprotein with other glycoconjugates imposes limitations on the interpretation of ultrastructural studies aimed at localizing a particular glycoprotein to a cellular site by using fluorescent or ferritin-labelled antisera. A radioimmunoassay inhibition technique for quantitative determination of the amounts of antigens in plants is also described.
