Assessment of cross-reactivity between Japanese cedar (Cryptomeria japonica) pollen and tomato fruit extracts by RAST inhibition and immunoblot inhibition

Background: An association between pollinosis and sensitivity to fruits and vegetables has been reported. Although Japanese cedar (Cryptomeria japonica) pollinosis is one of the most widespread diseases in Japan, there have been no reports demonstrating cross-reactivity between Japanese cedar pollen and other plant food. Objective: The aim of this study was to demonstrate cross-reactivity between Japanese cedar pollen and tomato fruit (Lycopersicon esculentum) using RAST inhibition and immunoblot inhibition. Methods: The RAST and immunoblot inhibition were performed using sera from patients with oral allergy syndrome (OAS) after ingesting fresh tomatoes. We identified some proteins that took part in cross-reactive IgE by the determination of N-terminal amino acid sequences and a homology search through the SWlSS-PROT database. Results: In the RAST inhibition, the bindings of IgE from the sera from four out of five (4/5) subjects to Japanese cedar pollen discs were inhibited by more than 50% by preincubation of the serum with tomato fruit extracts. Likewise, the IgE bindings to tomato fruit discs were inhibited more than 50% by Japanese cedar pollen extracts in 3/5 sera. In immunoblot inhibition, IgE binding activities of some protein bands on both membranes were decreased by heterologous inhibitors. However, the combinations of these protein bands involved in cross-reactivity were different between patients. Conclusion: We have demonstrated cross-reactivity between Japanese cedar pollen and tomato fruit using RAST inhibition and immunoblot inhibition.