Abstract

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease associated with aberrant activation of T and B lymphocytes for the production of inflammatory cytokines and autoreactive antibodies. Animal studies of SLE have indicated that Toll-like receptors (TLR) are important in the pathogenesis of murine lupus. In the present clinical study, differential protein expressions of TLR-1-9 of monocytes and different lymphocyte subsets from patients with SLE and normal control subjects were determined by flow cytometry. Results showed that the expression of intracellular TLRs (TLR-3, -8, -9) and extracellular TLRs (TLR-1, -2, -4, -5, -6) were elevated in monocytes, CD4(+) T lymphocytes, CD8(+) T lymphocytes and B lymphocytes of SLE patients compared to control subjects (all P < 0.001). Moreover, cell surface expression of TLR-4 on CD4(+) T lymphocytes and CD8(+) T lymphocytes, and TLR-6 on B lymphocytes, were correlated positively with SLE disease activity index (SLEDAI) (TLR-4 on CD4(+) T lymphocytes and CD8(+) T lymphocytes: r = 0.536, P = 0.04; r = 0.713, P = 0.003; TLR-6 in B lymphocytes: r = 0.572, P = 0.026). In concordance with the above results, there is an observable increased relative induction (%) of inflammatory cytokine interleukin (IL)-1beta, IL-6, IL-10 and IL-12, chemokines CCL2, CXCL8, CCL5 and CXCL10 from peripheral blood mononuclear cells (PBMC) upon differential stimulation by PolyIC (TLR-3 ligand), lipopolysaccharide (TLR-4 ligand), peptidoglycan (TLR-2 ligand), flagellin (TLR-5 ligand), R837 (TLR-7 ligand) and CpG DNA (TLR-9 ligand) in SLE patients compared to controls. These results suggest that the innate immune response for extracellular pathogens and self-originated DNA plays immunopathological roles via TLR activation in SLE.