Expression and significance of toll-like receptor 4 by peripheral blood mononuclear cell in rats with adjuvant-induced arthritis

Objective: To demonstrate the role of innate immunity reaction in rheumatoid arthritis and other autoimmune diseases by studying the expression of toll-like receptor 4 (TLR4) by peripheral blood mononuclear cell (PBMC) in rats with adjuvant-induced arthritis (AIA) and analyzing the relationship between expression of TLR4 by PBMC and score of arthritis severity. Methods: Both the proportion of CD14 +TLR4+ cells in CD14+ cells and the mean intensity of fluorescence (MIF) of TLR4+ cells were analyzed by flow cytometry. Expression of TLR4 mRNA by PBMC was determined by Northern blot. CD14+TLR4+/CD14+ ratio, TLR4 MIF and expression of TLR4 mRNA by PBMC in the model group at 15 days after AIA were compared, respectively, with normal control group and model group at 25 days. The correlation between TLR4 MIF and score of arthritis severity was analyzed by Mann-Whitey U test. Results: CD14+TLR4+/CD14+ ratio, TLR4 MIF and TLR4 mRNA expression in model group at 15 days after AIA were obviously increased compared with those in control and model groups at 25 days (P<0.01), and a good correlation between TLR4 MIF and score of arthritis severity was observed (15 d: r = 0.826, P<0.01; 25 d: r = 0.688, P<0.05), but no significant difference in model group at 25 days after AIA (P > 0.05). It indicated that TLR4 participated in the pathogenesis of rheumatoid arthritis. Conclusion: TLR4 expressed by PBMC is closely associated with pathogenesis and pathophysiology of rheumatoid arthritis, which suggests that innate immunity response plays an important role in pathogenesis of RA and other autoimmune diseases.