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 p otential threat to consumers due to their capacity to induce histamine rele ase from basophils. In this study, we analyzed the capacity of 16 common, i n 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 th e lectins, especially concanavalin A, lentil lectin, phytohemagglutinin, Pi sum sativum agglutinin and Sambucus nigra agglutinin, triggered basophils t o release IL-4 at concentrations of up to 1 ng/10(6) basophils. Lectins wit h high IL-4-inducing capacity also stimulated the release of IL-13 and hist amine. 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 bindin g as initial step of signal generation. In conclusion, several dietary lect ins can trigger human basophils to release IL-4 and IL-13. Since lectins ca n enter the circulation after oral uptake, they might play a role in induci ng the so-called early IL-4 required to switch the immune response towards a Th2 response and type I allergy.