Ses i 6, the sesame 11S globulin, can activate basophils and shows cross‐reactivity with walnut in vitro

Summary Background Sesame allergy is increasingly being reported, and multi‐sensitization to peanut and tree nuts has been described. The clinical relevance and cross‐reactivity of many sesame proteins, such as Ses i 6, are unknown. Objective The aims of this study were to perform a preliminary examination of the cross‐reactivity of Ses i 6 in vitro , examine the ability of Ses i 6 to activate basophils in a modified basophil activation test (mBAT), and assess whether such an assay may help to distinguish between potentially relevant and irrelevant IgE reactivity towards 11S globulin proteins. Methods Inhibition immunoblotting and chicken anti‐rJug r 4 antibodies were used to determine the cross‐reactivity of rSes i 6. Basophils from atopic donors were stripped of resident IgE before passive sensitization with food‐allergic sera and challenged with protein extracts or recombinant protein. Basophil activation was measured using two activation markers, CD203c and CD63, via flow cytometry. Results IgE immunoblotting showed cross‐reactivity between rJug r 4 and rSes i 6 using sera from two human donors and chicken IgY. Additionally, rSes i 6 activated basophils passively sensitized with sesame‐allergic sera. Cross‐reactive serum from a sesame‐allergic but walnut‐tolerant donor was not able to activate basophils when challenged by walnut extract despite IgE reactivity to walnut determined by immunoblotting. Conclusions The sesame 11S globulin shows partial immunological cross‐reactivity with walnut, and although it is classified as a minor allergen, activated basophils sensitized with serum from seven out of eleven sesame‐allergic donors. Additionally, the mBAT may help distinguish between clinically relevant and irrelevant in vitro IgE cross‐reactivity of seed storage proteins in nuts and seeds and thus warrants use in further studies.