The genus Saccharomyces includes industrial yeasts that are used for bread and alcoholic beverage production. Saccharomyces strains isolated from natural resources, referred to as "wild" yeasts, are used for making products with strain-specific flavors that are different from those of the "domesticated" industrial yeasts. The physiological effects of wild yeast are poorly understood. In this study, we isolated 2 Saccharomyces cerevisiae strains (S02 − 03) and 5 Saccharomyces paradoxus strains (P01 − 02, S01, S04 − 05) from natural resources in the Kiso area and investigated the effect of these fungal strains on IgE production by mouse spleen cells. Culturing spleen cells with heat-killed yeasts resulted in elevated IFN-γ and IL-12 levels followed by significant reduction in IgE levels. The S03 and P01 strains induced IL-12 p40 and IL-10 expression in RAW264 cells. Thus, wild strains of S. cerevisiae and S. paradoxus regulate macrophage cytokine production to improve the Th1/Th2 immune balance and suppress IgE production.

The oral intake of probiotic microorganisms has been investigated as a potential approach to prevent IgEassociated allergic diseases, including atopic dermatitis (AD). However, the effects of potentially edible wild yeast strains of the genus Saccharomyces on allergic symptoms remain poorly understood. In this study, we investigated the effects in the NC/Nga AD mouse model of Saccharomyces paradoxus P01 (P01), a wild strain selected based on its suppressive effect on IgE production in vitro. Compared to animals on a P01-free diet, mice fed a P01-supplemented diet had a markedly reduced incidence of skin lesions and picryl chloride-induced ear thickening and inflammation. Serum IgE levels and IgE production by spleen cells in mice fed the P01-supplemented diet were significantly lower than those of control mice. These results suggest that oral intake of specific IgE-suppressive wild strains of Saccharomyces yeast may be effective in suppressing IgE production and alleviating IgE-associated allergic symptoms.