Report - In vitro immune potentials of a water-soluble polysaccharide extract from Dioscorea opposita planted in Henan Province, China.

Dioscorea opposita is an edible and medicinal plant available in many areas of China. This study aimed to assess in vitro immune potentials of a water-soluble polysaccharide extract from D. opposita planted in Henan Province, China. In vitro effects of the extract on three immune cells (macrophages, natural killer cells and splenocytes) from mice and secretion of eight immune-related molecules in macrophages and splenocytes were evaluated. In total, the extract exhibited a dose-dependent manner on these immunological responses. The extract at dose level of 50μg/ml enhanced respective splenocyte proliferation, macrophage phagocytosis, and natural killer cell activity by 150%, 18% and 47%, increased secretion of interleukin-2 and interferon-γ (from 41.4 and 24.6 pg/ml to 48.8 and 91.5 pg/ml, respectively) but decreased secretion of interleukin-4 (from 38.9 to 27.9 pg/ml) in splenocytes. The extract at the same dose level also stimulated inducible nitric oxide synthase and lysozyme in macrophages, and enhanced secretion of interleukin-6, interleukin-1β and tumor necrosis factor-α (from 26.6, 73.4 and 39.6 pg/ml to 60.2, 131.0 and 144.7 pg/ml, respectively). It is concluded that water-soluble polysaccharides from D. opposita have immune potentials to the body, via activating immune cells and regulating the secretion of immune-related molecules.