Toll-like receptors and their role in host resistance to Toxoplasma gondii.

Toxoplasma gondii and other apicomplexan parasites are widely distributed obligate intracellular protozoa. A critical host mediator produced in response to T. gondii infection is IL-12. This cytokine is synthesized by dendritic cells, macrophages and neutrophils and plays a pivotal role in the production of IFN-gamma, which in turn activates anti-microbial effector cells. In the past several years, many of the receptors and signaling pathways that link pathogen detection to induction of IL-12 have been identified and characterized. Among these receptors the Toll-like receptor (TLR) family can recognize all classes of pathogens and induce different types of immune responses. In the following review, I summarize the evidence for specific TLR function in host resistance to T. gondii.