Pollen-wall proteins: release of the allergen antigen e from intine and exine sites in pollen grains of ragweed and Cosmos

Cytochemical staining methods and immunofluorescence techniques have been used to follow the release of proteins, including the allergen Antigen E, from whole pollen of ragweeds (Ambrosia spp.) and Cosmos bipinnatus (Compositae). These proteins have been detected in 2 sites in the wall: in the inner cellulosic intine layer especially at the germinal apertures, and in the cavea and the cavities of the outer exine layer, the sexine. It was found that the release of exine-associated proteins, including the allergenic fraction, begins within 2 s of contact with aqueous media, the loss being mainly through the micropores of the tectum at the bases of the sexine spines. The intine proteins were emitted more slowly, discharge beginning at the colpi after 1 min of moistening. So far as can be judged from the methods used, most of the mobile protein lost from the pollen of Cosmos on hydration comes from the exine and is therefore sporophytic in origin, while in the ragweeds the bulk comes from the intine in the neighbourhood of the germinal apertures, and so is gametophytic.