Effects of oral administration of Yam tuber storage protein, dioscorin, to BALB/c mice for 21-days on immune responses

Dioscorin, the tuber storage protein of yam, was reported to have immunomodulatory activity in RAW264.7 murine macrophage cell lines (Food and Chemical Toxicology, 2007, 45, 2312-2318). However, the immunomodulatory function of dioscorin after being ingested was not elucidated in vivo. Hence, BALB/c mice were given oral dioscorin (2.5 and 20 mg/kg/day) once a day for 21-days. Lymphocyte subpopulation changes in the peripheral blood and splenocytes, stimulation in phagocytosis of the polymorphonuclear cell (PMN) and monocytes, the natural killer (NK) cell cytotoxicity, the splenocyte proliferation, and cytokine secretions in the presence of PHA were determined. The number changes of Peyer's patches and secreted IgA (slgA) in the feces were determined. Oral dioscorin for 21-days increased the subpopulation in natural killer cells (CD49⁺) and/or B cells (CD19⁺), elevated the phagocytosis of PMN (p<0.01) and MON (p<0.01), and the NK cell cytotoxic activity (p<0.05), and stimulated splenocyte proliferations in the presence of LPS or PHA (p<0.05) in comparison with those of the control. Cytokines of INF-y, IL-4, and IL-10 secretions, the numbers of Peyer's patches, and slgA in the feces showed higher levels in oral dioscorin and significant difference to those of the control (p < 0.001 ). These results suggested that dioscorin exhibited systemic and mucosal immunomodulatory activities after being ingested in vivo.