The lectin reactivity and lectin-like activity of allergenic pollen extracts

The binding of soluble components of pollen grains to plant-stigma receptors can be inhibited by concanavalin A. This lectin-like activity of pollen components is important in the genetic control of plant reproduction. Aqueous extracts of allergenic pollens also react with concanavalin A. Agarose gel-diffusion precipitates were used to survey and characterize the ability of allergenic pollen extracts to react with concanavalin A and other lectins. Concanavalin A alone precipitated with extracts of plantain, American beech, white ash, and corn pollens. Surprisingly, extracts of the pollen from certain plants also precipitated when the extracts were diffused against pollen extracts from other plants. Pollen extracts of alfalfa, white ash, American beech, burweed marsh elder, redtop grass, corn, plantain, orchard grass, and aspen reacted with one or more other pollen extracts. Extract precipitin activity was reliably obtained after extracting pollens for 20 min with pH 7.5, 0.05M Tris buffer in 0.2M of saline. Optimal agarose gel conditions for detecting the precipitin reactions were pH 8.5 to 9.0, 75 mM borate buffer made to an ionic strength of 1.5M with NaCl for concanavalin A pollen reactions and 0.015M with NaCl for pollen-pollen reactions. The presence of the borate ion was necessary for optimal detection of the agarose gel precipitates. Studies of the inhibition of the lectin-pollen and pollen-pollen reactions with specific mono and disaccharides revealed many similarities and differences between the two types of reactions. The high concentrations of glycerol used to stabilize pollen extracts also inhibit these reactions.