Diosgenin, a steroidal sapogenin, enhances antigen-specific IgG2a and interferon-γ expression in ovalbumin-sensitized BALB/c mice

The effect of diosgenin, the most abundant sapogenin in Chinese yam, on humoral immunity was investigated. Ovalbumin (OVA)sensitized and challenged BALB/c mice were administered daily with diosgenin for 34 days. The production of OVA-specific serum IgG(2a) was significantly enhanced by diosgenin treatment, whereas total IgE and OVA-specific IgG(1), IgG(2a) and IgM were unaffected. In parallel with the enhancement of IgG(2a), OVA-induced IFN-gamma secretion and mRNA expression were markedly elevated in splenocytes of diosgenin-treated mice, whereas IL-4 expression was unaltered. Furthermore, the expression of T-bet, but not of GATA-3, in splenocytes was up-regulated by diosgenin administration. However, diosgenin treatment did not modulate IL-4 mRNA expression and inflammatory cell infiltration in the lung of OVA-sensitized and challenged mice. Collectively, these data suggest that diosgenin regulates the systemic immune response towards the Th1 direction in response to OVA sensitization. The present study provides evidence to show that intake of diosgenin modulates certain aspects of acquired immunity, including the enhancement of antigen-specific IgG2a and IFN-gamma expression, which may be mediated through the up-regulation of Th1 differentiation.