Mast cells are inflammatory cells that respond to signals of innate and adaptive immunity with immediate and delayed release of mediators. ArtinM, a lectin from Artocarpus integrifolia with immunomodulatory activities, is able to induce mast cell activation, but the mechanisms remain unknown. This study sought to further investigate the effects of the lectin on mast cells. We showed that ArtinM binds to mast cells, possibly to the high affinity receptor for immunoglobulin E (IgE) - Fc epsilon RI - and/or to IgE bound to Fc epsilon RI. Binding of the lectin resulted in protein tyrosine phosphorylation and release of the pre- and newly-formed mediators, beta-hexosaminidase and LTB(4) by mast cells, activities that were potentiated in the presence of IgE. ArtinM also induced the activation of the transcription factors NF kappa B and NFAT, resulting in expression of some of their target genes such as IL-4 and INF-alpha. In view of the established significance of mast cells in many immunological and inflammatory reactions, a better understanding of the mechanisms involved in mast cell activation by ArtinM is crucial to the pharmacological application of the lectin. (C) 2011 Elsevier Inc. All rights reserved.