Immunomodulatory effects of type II arabinogalactans fraction from Anoectochilus formosanus in a murine model of OVA-induced airway hyperresponsiveness

Polysaccharides have been investigated for their potential role in modulating allergic asthma, a chronic respiratory disease characterized by airway hyperresponsiveness (AHR). This study aimed to evaluate the immunomodulatory effects of a type II arabinogalactan fraction from Anoectochilus formosanus (AGAF) on allergic responses in a murine model of ovalbumin (OVA)-induced allergic asthma. BALB/c mice were treated with various doses of AGAF (350, 700, and 1750 mg/kg), while the control groups received either distilled water (negative control) or prednisolone (10 mg/kg, positive control) over a six-week preventive regimen. After this period, mice were challenged with OVA to examine the immunomodulatory effects of AGAF. We investigated cellular differentiation and proliferation in lymphoid organs, anti-ovalbumin immunoglobulin levels, bronchial hyperresponsiveness, lung inflammation, histopathological changes and immunohistochemical analysis of TSLP, JNK and TGF-β1 in lungs. Six weeks of AGAF administration significantly downregulated thymic stromal lymphopoietin (TSLP) and c-Jun N-terminal kinase (JNK) expressions in the airways, reduced airway inflammatory cell infiltration, inhibited mast cell degranulation, decreased mucus production, modulated T helper (Th)1/Th2 differentiation, lowered anti-OVA IgE levels, and alleviated bronchoconstriction. These findings suggest that AGAF can influence T and B cell development and modulate allergic responses, making it a potential therapeutic agent for allergic asthma.