Suppression of Th2 Immune Responses by Mekabu Fucoidan from Undaria pinnatifida Sporophylls

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Abstract
We demonstrated that mekabu fucoidan obtained from Undaria pinnatifida (Up) sporophylls augments the type 1 T-helper (Th1) cell response in normal BALB/c mice. In this study, we examined the effects of the fucoidan of mekabu on the type 2 T-helper (Th2) response in bronchoalveolar lavage fluid (BALF) after ovalbumin (OVA) aerosol challenge. Mekabu fucoidan (50 mg/kg) was injected intraperitoneally into BALB/c mice for 4 days, and then the mice were sensitized with 50 microg/mouse of OVA plus alum (1 mg/mouse) 1 and 8 days later. The mice were challenged with OVA delivered using a nebulizer 7, 8 and 9 days after the second challenge with OVA plus alum. After 24 h, we assessed T cell responses in BALF by measuring the amount of Th2 cytokines (IL-4, IL-5, IL-13) and gamma-interferon (IFN-gamma) produced by Th1 cells. The production of Th2 cytokines was suppressed (p < 0.05), and the amount of IFN-gamma was not increased in the mice treated with mekabu fucoidan. Anti-OVA immunoglobulin E (IgE) and IgE levels in serum determined after challenge with aerosolized OVA at the end of the experiment were lower (p < 0.05) in the treated than in the control mice. The pulmonary inflammation was relieved by mekabu fucoidan, which also downregulated Th2-dominated responses. These results indicate that mekabu fucoidan modulates Th2 responses and might be useful for treating allergic inflammation.