Toll-like receptor expression in lupus peripheral blood mononuclear cells

OBJECTIVE: To investigate expression of members of the Toll-like receptor (TLR) family in peripheral blood mononuclear cells (PBMC) in patients with systemic lupus erythematosus (SLE). METHODS: We analyzed PBMC from 14 patients with SLE and 15 healthy subjects. The surface expressions of TLR2 and TLR4 and intracellular expression of TLR9 on PBMC were analyzed by flow cytometry. RESULTS: Although TLR4 expressions on CD14+ monocytes were not significantly different between healthy subjects and patients with SLE, TLR2 expressions on monocytes were reduced in patients with SLE compared to healthy subjects. Intracellular TLR9 expression levels of CD19+ B lymphocytes were significantly elevated in patients with SLE. However, the TLR9 expression levels of plasmacytoid dendritic cells were not significantly different between these patients and healthy subjects. CONCLUSION: Our results show that human peripheral blood B cells express TLR9 and that its expression is increased in patients with SLE. This upregulated expression of TLR9 in B cells may be related to the abnormal B cell hyperactivity in patients with SLE.