Expression and Functional Analysis of Toll-Like Receptors of Peripheral Blood Cells in Asthmatic Patients: Implication for Immunopathological Mechanism in Asthma

We investigated the expression profile of toll-like receptors (TLRs) and TLR ligand-activated production profile of asthma-related inflammatory cytokines in asthmatic patients. The expression of TLR1-8 on monocytes, CD4+ T helper lymphocytes, CD8+ T cytotoxic lymphocytes, CD19+ B lymphocytes, and dendritic cells, and ex vivo production of cytokines from peripheral blood mononuclear cells activated by TLR ligands were measured by flow cytometry. Ex vivo productions of TNF-alpha, IL-10, and IL-1 beta by TLR4 and TLR5 ligand LPS and flagellin were significantly lower in asthmatic patients (all P < 0.05). Expression of TLR4 and TLR5 was also found to be significantly lower in asthmatic patients when compared to that of control subjects (all P < 0.05). Therefore, the decreased activation of TLR4 and TLR5 in asthmatic patients might contribute to the immunopathological mechanisms of asthma by reducing the release of Th1 and anti-inflammatory cytokines.