Food allergens are protected from degradation during CD23-mediated transepithelial transport

Background: CD23 (FcεRII) is expressed by intestinal epithelial cells (IEC) following allergic stimulation and increases the uptake of IgE/allergen complexes. The aim of this study was to further analyze the role of CD23 in the intraepithelial processing of food allergens during transepithelial transport. Methods: Balb-C mice were sensitized intraperitoneally with horseradish peroxidase (HRP) or β-lactoglobulin (β-LG) in the presence of pertussis toxin. In control and sensitized mice, ³H-HRP, intact HRP, or ¹⁴C-β-LG fluxes were measured across jejunal segments mounted in Ussing chambers, in the presence or absence of mucosal anti-CD23 antibodies. HPLC analysis of serosal buffer was performed to detect HRP- or β-LG-derived radiolabelled metabolites generated during transepithelial transport. Results: In HRP-sensitized mice, ³H-HRP fluxes and intact HRP fluxes (3,836 ± 476 and 290 ± 86 ng/h·cm², respectively) were significantly increased compared to control mice (1,677 ± 297 ng/h·cm², p < 0.01, and 106 ± 23 ng/h ± cm², p < 0.02, respectively). HPLC analysis indicated the presence of intact HRP in the serosal compartment already 10 min after addition of HRP to the mucosal compartment, a result not observed in the control mice. In the presence of anti-CD23 antibodies, intact HRP fluxes were significantly decreased (131 ± 27 ng/h·cm²) compared to control values in sensitized mice (290 ± 86 ng/h·cm², p < 0.02), suggesting that CD23 is involved is this 'protected' transport pathway. A similar protection during intestinal transport was observed for β-LG in β-LG sensitized mice. Conclusions: These results confirm that CD23 is involved in the rapid transepithelial transport of intact allergens in sensitized animals, and indicate that CD23 opens a 'protected' transport pathway in IECs.