Toll-like receptor (TLR) 2 and TLR4 deficiencies exert differential in vivo effects against Schistosoma japonicum.

Little is known about the functions of Toll-like receptor 2 (TLR2) and TLR4 in innate/acquired responses to Schistosoma japonicum. Through in vivo study, the contributions of TLR2 and TLR4 to host immune responses during S. japonicum infection were investigated. Early infection experiments showed higher protein and mRNA levels of IL-12, IFN-γ and IL-4 in dermal tissues and retroauricular draining lymph nodes respectively in TLR2(-/-) mice on day four post-infection and opposite changes in TLR4(-/-) mice. In the acute infection with S. japonicum for 6 weeks, TLR2(-/-) mice manifested lower egg burden as well as the enhancement of T cell activation and upregulated expression of some cytotoxic genes, as assayed by Th1/Th2 cytokine secretion and DNA microarray analysis. Also, the opposite parasitological and immunological effects were observed in TLR4(-/-) mice. These results demonstrate that during S. japonicum infection, TLR2 and TLR4 might direct distinct adaptive immune responses since the early stage, which may lead to different infection outcomes.