The essential role played by Toll-like receptors (TLRs) during parasitic infections, as a part of the innate immune response, has gained much attention. TLR-induced signaling pathways can eradicate invading pathogens. However, uncontrolled activation of TLR leads to tissue damage. Therefore, negative regulation of TLRs results in diminished pro-inflammatory cytokine production and limits excessive pathology. This review outlines the interplay between TLR-mediated responses and some parasitic infections that involve both activation and negative regulation of TLRs. Furthermore, the promising role of TLRs in both therapeutic strategies and vaccine development for parasitic infections will be highlighted. Moreover, treatment of other diseases, for example, inflammatory bowel diseases, using parasite-derived TLR ligands has initiated a new era in immunotherapy.

Many epidemiological data support the postulate that infection with helminths might provide some protection against allergic and autoimmune diseases. Hence arises the concept that helminths strongly influence the immune system and enable protective pathways against these hyperimmune-associated disorders. This review discusses how Trichinella spiralis can make the immune system smarter in dealing with hyperimmune-associated disorders. T. spiralis possesses the capacity to direct the immune system towards a mixed Th1/Th2 phenotype with predominance of Th2 response, or it may interfere with dendritic cell maturation, induce the alternatively activated macrophages and elicit the regulatory arm of the immune response via Treg or regulatory B cells.