Moderate consumption of alcoholic beverages is suggested to reduce cardiovascular risk. Within this context, most attention is drawn to antioxidant ingredients of wine, but also beer was found to be beneficial. Potential effects of three different types of beer including alcohol-free beer were investigated using freshly isolated human peripheral blood mononuclear cells stimulated with the mitogen phytohaemagglutinin in vitro. Neopterin production and tryptophan degradation were monitored in culture supernatants to determine effects of test substances on immunobiochemical pathways induced by interferon-gamma. In a subgroup of experiments also production of interferon-gamma was measured. Compared to unstimulated cells, phytohaemagglutinin increased production of neopterin and also triggered the degradation of tryptophan (all p < 0.01). All types of beer (2-4% dilution) were found to counteract these stimulation-induced effects and significant reduction of neopterin formation and tryptophan degradation was observed (p < 0.01). Data demonstrate that beer reduces production of neopterin and degradation of tryptophan, both these biochemical pathways are induced during cell-mediated immune response. Data suggest that the immunosuppressive capacity of beer may relate to its anti-inflammatory nature.