Mononuclear cell response to enterobacteria and Gram-positive cell walls of normal intestinal microbiota in early rheumatoid arthritis and other inflammatory arthritides.

Objective: To study whether enterobacteria and Gram-positive bacterial cell walls (BCW) derivedfrom normal intestinal microbiota are involved in the etiopathogenesis of early rheumatoid arthritis (RA).

Methods: Peripheral blood mononuclear cells (PBMC) and synovial fluid mononuclear cells (SFMC) were isolatedfrom patients with early RA (the average duration of 5 months) and the controls (other types of inflammatory arthritis). The mononuclear cell proliferation and tumor necrosis factor-alpha (TNF-alpha) responses to heat-killed Salmonella enteritidis (SE). Yersinia enterocolitica (YE), and Escherichia coli (EC), and to Gram-positive BCW derived from four common intestinal indigenous bacteria, Eubacterium aerofaciens (EA), Eubacterium limosum (EL), Lactobacillus casei (LC), and Lactobacillus fermentum (LF), and a BCW derived from a pathogen, Streptococcus pyogenes (SP) were investigated.

Results: 39% or 56% of patients with early RA showed significant proliferation responses by PBMC or SFMC against enterobacteria, respectively. In other types of arthritis, corresponding figures were 59% or 66%. When BCW were used as antigens, 8.1% or 23% of patients with early RA showed proliferation responses by PBMC or SFMC, respectively. In other types of arthritis the corresponding figures were 7.5% or 35%, respectively. However, TNF-alpha production by SFMC stimulated by EA BCW, SE, YE or EC, was significantly higher in early RA than in other types of arthritis.

Conclusions: These results suggest that SFMC reacting with enterobacteria or BCW exist in some patients with early RA, but also in other types of inflammatory arthritis. Intestinal bacterial agents may play a role in the etiopathogenesis of RA, but the effect appears to be non-specific.