Dietary lectins can induce in vitro release of IL-4 and IL-13 from human basophils.

Dietary lectins, present in beans and other edible plant products, pose a potential threat to consumers due to their capacity to induce histamine release from basophils. In this study, we analyzed the capacity of 16 common, in particular dietary, lectins to induce human basophils to secrete IL-4 and IL-13, the key promoters of Th2 responses and IgE synthesis. Several of the lectins, especially concanavalin A, lentil lectin, phytohemagglutinin, Pisum sativum agglutinin and Sambucus nigra agglutinin, triggered basophils to release IL-4 at concentrations of up to 1 ng/10(6) basophils. Lectins with high IL-4-inducing capacity also stimulated the release of IL-13 and histamine. Lectin-induced IL-4 and IL-13 release reached a maximum after 4-6 h and more than 18 h, respectively. Affinoblotting revealed that lectins with the capacity to induce mediator release bind to IgE, suggesting IgE binding as initial step of signal generation. In conclusion, several dietary lectins can trigger human basophils to release IL-4 and IL-13. Since lectins can enter the circulation after oral uptake, they might play a role in inducing the so-called early IL-4 required to switch the immune response towards a Th2 response and type I allergy.