It has long been recognized that inflammation to dermatophyte infection is different among various hosts, but the mechanism underlying is still not well understood. Toll-like receptor (TLR2), mediates the innate immune response against dermatophyte infection and is very important to trigger the inflammatory response to dermatophytes. Considering the different amino acid sequences and structures of TLR2, we speculated that TLR2 from different hosts will activate the downstream signal pathways to varying degrees, resulting in different inflammatory responses to dermatophytes.
In this study, we constructed the mice-human fusion TLR2 expressed HaCaT (mhTLR2-HaCaT) by replacing the extracellular ligand recognition region of human TLR2 with that of the mouse. Then hTLR2-HaCaT cells and mhTLR2-HaCaT cells were infected with T. rubrum and M. canis for 24 h followed by immunoblotting to asses associated proteins of p38 and JNK signal pathway.
Compared with that of human TLR2 expressed HaCaT (hTLR2-HaCaT), levels of phosphorylated p38 protein were increased in mhTLR2-HaCaT cells stimulated by T. rubrum for 24 h, and levels of phosphorylatedJNK and c-Jun protein were increased in mhTLR2-HaCaT cells whenstimulated with M. canis for 24 h.
Compared with hTLR2-HaCaT cells, p38 and JNK signal pathwayswere activated in mhTLR2-HaCaT after being infected by Trichophyton rubrumand Microsporum canis, respectively. Since p38 and JNK are the mainpathways that transduce the signal for host recognition of dermatophytes andmediate the downstream inflammatory response, it suggested that theinterspecific difference of TLR2 ectodomain may be one of the reasons for thedifferent inflammatory manifestations between humans and mice infected bythese two dermatophytes. Quite especially, the mouse-derived TLR2extracellular recognition region is more effective in recognizing T. rubrum andM. canis to activate the downstream signal pathways, resulting in a tenserinflammatory response against these two dermatophytes.