Expression of toll-like receptors on antigen-presenting cells in patients with falciparum malaria.

The continuous release of blood-stage malaria parasites and their products can activate components of the innate immune system and induce the production of proinflammatory cytokines. Toll-like receptors (TLRs) have emerged as pattern-recognition receptors, residing on/in innate immune cells whose function is recognizing specific conserved components on different microbes. The aim of this study was to determine the expression of TLR2, TLR4 and TLR9 on antigen-presenting cells (APCs) in patients with mild and severe forms of falciparum malaria. Healthy individuals were used as controls. Peripheral blood mononuclear cells (PBMCs) were stained with specific monoclonal antibodies (mAbs) to investigate the percentage and the level of TLR expression by flow cytometry. Patients with severe and mild malaria showed increased surface expression of TLR2 and TLR4 on CD14(+)monocytes and myeloid dendritic cells (MDCs) and decreased intracellular expression of TLR9 on plasmacytoid dendritic cells (PDCs), compared to those of healthy controls. A significant decrease in the percentage of circulating CD14(+)monocytes and MDCs expressing TLR2 was found in both severe and mild malaria patients. These findings suggested that TLRs might play role in innate immune recognition in which the differential expression of TLRs on APCs could be regulated by the P. falciparum parasite.