Using Human Basophil Donors to Assess the Clinical Relevance of Sesame 11S Globulin, Ses i 6

Abstract

RATIONALE: Human basophil donors were used in a modified basophil activation test (BAT) to determine the clinical relevance and cross reactivity of the sesame 11S globulin protein, Ses i 6. METHODS: Using venous blood from atopic non-food allergic subjects basophils were enriched in a single step using a discontinuous percoll gradient. Basophils were stripped of resident IgE before passive sensitization with food allergic sera and challenged with whole extract and recombinant protein. Antibodies against cd203c and cd63 were used as fluorescent labels; activation was measured on a flow cytometer. Inhibition immunoblotting was used to determine IgE cross-reactivity with the recombinant 11S walnut globulin protein rJug r 4. Serum IgE from walnut or sesame food allergic donors was pre-absorbed overnight with walnut or sesame proteins. RESULTS: Inhibition immunoblotting showed cross-reactivity between the 11S globulin proteins of sesame and walnut. Additionally, rSes i 6 was able to increase expression of activation markers on basophils passively sensitized with sesame allergic sera compared to controls. Cross-reactive serum from a sesame allergic donor who tolerates walnuts was not able to activate basophils despite walnut IgE reactivity determined by immunoblotting. CONCLUSIONS: The sesame 11S globulin appears to be a clinically relevant food allergen as determined by a modified BAT using human basophil donors and passive sensitization. Additionally, the modified BAT may be able to distinguish between clinically irrelevant and relevant in vitro IgE cross-reactivity of seed storage proteins in nuts and seeds and may thus be an important tool in further studies.