Roles of major oligosaccharides on Cry j 1 in human immunoglobulin E and T cell responses

Background: We have demonstrated that carbohydrates in Cry j 1, the major allergen of Cryptomeria japonica pollen, play a major role in promoting Cry j 1-specific Th2 response. However, little is known as to whether the carbohydrates directly participate in allergic responses. Objective: We sought to determine whether Cry j 1-related oligosaccharides function as IgE and/or T cell epitopes. In addition, the regulatory effect of Cry j 1-related oligosaccharide on Cry j 1-specific T cell responses was investigated. Methods: Two monovalent oligosaccharides largely found on Cry j 1, Manα1- 6(Manα1-3) (Xylβ1-2)Manβ1-4GlcNAcβ1-4(Fucα1-3)GlcNAc (M3FX), and GlcNAcβ1-2Manα1-6(GlcNAcβ1-2Manα1-3) (Xylβ1-2)Manβ1-4GlcNAcβ1-4(Fucα1-3)GlcNAc (GN2M3FX) were prepared. Manα1-2Manα1-6(Manα1-2Manα1-3)Manα1- 6(Manα1-2Manα1-2Manα1-3)Manβ1-4GlcNAcβ1-4GlcNAc (M9A) was used as control. Competitive inhibition ELISA for Cry j 1-specific IgE was performed using these oligosaccharides as inhibitors. In addition, T cell lines specific for Cry j 1 or purified protein derivative of Mycobacterium tubecurosis (PPD) were established, and cellular responses against these oligosaccharides were investigated in the presence or absence of the respective antigens. Results: Overall, neither M3FX nor GN2M3FX displayed inhibitory effect on the binding between IgE and Cry j 1. In addition, M3FX did not by itself stimulate Cry j 1 or PPD-specific T cells. However, M3FX significantly inhibited Cry j 1-induced proliferation and IL-4 production in Cry j 1-specific T cells. Such an inhibitory effect was not seen in PPD-specific T cell responses. Conclusion: These results suggest that Cry j 1-related oligosaccharides are not major epitopes for IgE or T cells. However, these oligosaccharides have a novel potential to inhibit Cry j 1-specific T cell responses selectively.