Effects of a Hydrosoluble Bacterial Extract from Escherichia Coli (OM-89) on Cytokine Production by Peripheral Blood Mononuclear Cells from Healthy Subjects and Patients with Rheumatoid Arthritis

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Abstract
OM-89 is a bacterial extract from escherichia coli, proposed as an immunomodulating drug for the treatment of rheumatoid arthritis (RA). Since immunological mechanisms may play a role in its action, the immunological effects of OM-89 were evaluated in vitro on peripheral blood mononuclear cells (PBMC) derived from healthy subjects and RA patients. Results indicated that in the absence of OM-89, production of the monokines interleukin-1β (IL-1β) and tumor necrosis factor-a (TNF-α) is increased, while that of the lymphokines interleukin-2 (IL-2) and interferon-γ (IFN-γ is decreased by phytohemagglutinin (PHA)-stimulated PBMC from RA patients as compared with PBMC from healthy subjects. In the presence of PHA, OM-89 enhanced the production of IL-1β TNF-α, IL-2, and IFN-γ. IL-1β and IL-2 curves obtained using increasing amounts of OM-89 did not differ depending on the source of PBMC. By contrast, in the presence of increasing amounts of OM-89, TNF-α secretion significantly higher and IFN-α secretion significantly lower with PBMC from RA patients compared to PBMC from healthy subjects. These data indicate that OM-89 acts on monocytes and T cells directly and/or indirectly and suggest a possible clinical activity by OM-89 in RA relative to its immunological properties.