Immune Modulators as Antiviral Agents

Immune system effects of echinacea, ginseng, and astragalus: a review

Traditional herbal medicine provides several remedies for strengthening the body's resistance to illness through effects on immune system components. This review article examines 3 popular herbal immune stimulants that are often of interest to cancer patients. Echinacea, a native of North America, is widely used to prevent, or provide early treatment for, colds. Preclinical studies lend biological plausibility to the idea that echinacea works through immune mechanisms. Numerous clinical trials have been carried out on echinacea preparations: it appears that the extracts shorten the duration and severity of colds and other upper respiratory infections (URIs) when given as soon as symptoms become evident. However, trials of long-term use of echinacea as a preventive have not shown positive results. Ginseng has been studied in some depth as an antifatigue agent, but studies of immune mechanisms have not proceeded so far. Preclinical evidence shows some immune-stimulating activity. There have been several clinical trials in a variety of different diseases. Astragalus is the least-studied agent. There are some preclinical trials that show intriguing immune activity. The herbs discussed appear to have satisfactory safety profiles. Cancer patients may wish to use these botanicals to inhibit tumor growth or to boost resistance to infections. However, passive immunotherapy with herbs, with no mechanism to expose tumor antigens, is unlikely to be effective in inhibiting tumor growth. Although the margin of safety for these herbs is large, more research is needed to demonstrate the clear value of using herbs to improve resistance to infections.

Immunomodulatory action of levamisole--II. Enhancement of concanavalin A response by levamisole is associated with an oxidation degradation product of levamisole formed during lymphocyte culture

Previously we determined that levamisole (LMS), when stored for a period of time, breaks down to three degradation products at neutral and alkaline pH. At low concentrations (10(-6) M), Product 1 inhibits the lymphocyte response to concanavalin A (Con A). Product 2 enhances the response and Product 3 has no effect. At higher concentrations (10(-5) M) all three products inhibit the response. To determine if these products are formed in culture media under culture conditions (e.g. in RPMI-1640 bicarbonate buffered medium, 37 degrees C, pH 7.0-7.5, during a 72 h culture period), we added freshly prepared LMS solutions to culture media with and without lymphocytes present and maintained the pH at 7.0, 7.25 or 7.5 by varying the amount of CO2 present. Periodically over a 72 h period, aliquots of the media were removed and analyzed for the presence of LMS and the three degradation products. Within 4 h, two of the degradation product began to form in culture media with or without lymphocytes present. Product No. 1, 3-(2-mercaptoethyl)-5-phenylimidazolidine-2-one or dl-2-oxy-3-(2-mercaptoethyl)-5-phenylimidazolidine (OMPI), which inhibits the lymphocyte response to concanavalin A (Con A) at concentrations above 0.4 micrograms/ml, was formed at pH 7.0, 7.25 and 7.5, but the compound did not reach inhibitory concentrations in the lymphocyte cultures during the 72 h culture period. Product No. 2, 6-phenyl-2,3-dihydroimidazo (2,1-b) thiazole, which enhances the Con A response between concentrations of 0.5 and 10 micrograms/ml, was detected at concentrations between 2.5 and 3.5 micrograms/ml at pH 7.25 and 7.5. Product 2 was not detected in cultures at pH 7.0 and subsequently when we cultured lymphocytes with freshly prepared LMS and maintained the pH at 7.0, no significant enhancement of the Con A response was observed.(ABSTRACT TRUNCATED AT 250 WORDS)