Background. Allergic rhinitis (AR) is a disease characterized by IgE-mediated, allergic inflammation of the nasal mucosa. T helper (Th) 2 cells play an important role in the development of IgE-mediated diseases such as AR, with local overproduction of Th2 cytokines (IL-4, IL-5 and IL-13) at the site of allergic inflammation. Th1 cytokines (IL-12 and IFN-γ) are known to suppress this Th2 immune response, aiding the treatment of these diseases. β-1,3-1,6-glucan (Glucan) is an immunomodulator stimulating particularly the antitumor response. An efficient antitumor stimulation can be achieved through a Th1-mediated immune response.
Objective. The aim of this study was to investigate the effects of Glucan on the immunopathogenic processes in the microenvironment to determine if it reverses the Th2-mediated immune response in AR to Th1-mediated response.
Methods. 24 Olea europea mono-sensitized patients with AR were randomized into Glucan and placebo groups. The Glucan group consisted of 12 patients who received Glucan treatment for 12 weeks, while the placebo group of 12 patients received placebo during the same period. A nasal provocation test (NPT) with Olea europea was performed at the beginning and end of treatment, and nasal lavage followed the positive NPT. IL-4, IL-5, IFN-γ and IL-12 levels and the eosinophil count (%) were measured in nasal lavage fluid (NLF) samples. Simultaneously, peripheral blood eosinophil % values were measured.
Results. After treatment, IL-4 and IL-5 levels in NLF from the Glucan group were found to have decreased significantly (p = 0.027, p = 0.04; respectively), while IL-12 levels were found to have significantly increased (p = 0.008). However, IFN-γ levels had not changed. On the other hand, none of the cytokine levels had changed significantly in the placebo group following treatment. Moreover, the percentage of eosinophils in the NLF was found to have decreased significantly after treatment in the Glucan group (p = 0.01), while that of the placebo group did not change. Peripheral blood percentage eosinophil levels had not changed significantly in any group.
Conclusion. Th2-originated IL-4 and IL-5 levels responsible for the allergic inflammatory response in the microenvironment of patients with AR, are decreased with Glucan while levels of Th1-originated IL-12 are increased. Moreover, eosinophils, which are important effector cells of the inflammatory response, are decreased in the microenvironment. As a result, Glucan may have a role as an adjunct to standard treatment in patients with AR.