Research U pper respiratory tract infections are a major source of morbidity throughout the world; in the United States alone at least 1 billion colds per year have been reported, with a frequency of 2-6 colds per person. 1 Finding effective ways to reduce the frequency of these infections is therefore an important issue. Agents such as analgesics, antihistamines and decongestants have been found to be ineffective because of their limited efficacy against specific symptoms, 2 whereas safety concerns for some antiviral drugs limit their use. 3,4 Natural health products with properties that stimulate the immune system have been used to combat the common cold, but the results are often inconsistent. 5 Extracts of North American ginseng (Panax quinquefolium) containing polysaccharides and oligosaccharides have been shown to have immunomodulatory effects. [6][7][8][9][10][11][12] These extracts have been shown to enhance immune responses such as immunoglobulin production by lymphocytes and natural immune responses by peritoneal exudate macrophages. 6 They have also been found to enhance anticomplementary and reticuloendothelial system activities, 7 enhance macrophage Fc receptor expression, 8 increase the phagocytosis index along with phagocytosis fraction, 9 and induce messenger RNA expression of interleukin-2 (IL-2), interferongamma (IFN-γ), interleukin-1α and granulocyte-macrophage colony-stimulating factor as well as lymphokine-activated killer cells and CD8+ cells. 10 In addition, these extracts appear to stimulate cell-mediated immune response and natural killer cell cytotoxicity 11 as well as to have cytotoxic effects on a wide range of tumour cell lines without major histocompatibility complex restriction. 12 Recently, a patented poly-furanosyl-pyranosyl-saccharide-rich extract of North American ginseng (COLD-fX, CV Technologies Inc., Edmonton) was also shown to be capable of enhancing lymphocyte function and initiating acquired immune responses. 13 In a recent study on human peripheral blood mononuclear cells cultured with live influenza virus, the extract was shown to be effective in enhancing the production of IL-2 and IFN-γ (unpublished data). IL-2 and IFN-γ are major T-cell and natural killer cell cytokine responses associated with virus-elicited adaptive immunity, and IFN-γ

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