Immunomodulating Effect of Living Nonpathogenic Enterococcus faecalis Originated from Humans Symbioflor 1 is a pharmaceutical preparation, consisting of a suspension of living nonpathogenic Enterococcus faecalis (E. faecalis). The effect on the liberation of cytokines of E. faecalis was investigated in in-vitro experiments with human peripheral mononuclear blood cells revealing the following results: 1. E. faecalis stimulates the liberation of interleukin 1 (IL-1 beta) and interleukin-6 (IL-6) in a dose-dependent manner; the E. faecalis induced liberation of IL-1 beta and IL-6 is inhibited by dexamethasone (Dm) but not by cyclosporin A (CsA). 2. E. faecalis stimulates the liberation of gamma-interferon (IFN-gamma) in a dose-dependent manner, which is inhibited by both Dm and CsA. 3. Phytohemagglutinin (PHA)-induced liberation of gamma-IFN and interleukin-2 (IL-2) is inhibited by E. faecalis in a dose-dependent manner. The relevancy to clinical trials of the in vitro results is discussed.