|Activation of antigen presenting
cells (APCs) by LPS or dsRNA results in heterodimerization of Trif/Tram
(TLR4) or homodimerization of Trif (TLR3) leading to the subsequent activation
of MAP kinases and NF-kB but also to activation of the IRF3 pathway. Activated
IRF3 translocates to the nucleus and results in transcription of IFN-b.
In turn IFN-b is secreted and activates type I IFN receptor (IRFRA1,2) in
an atocrine or paracrine way. Activation of the type I IFN receptor results
in the upregulation of costimulatory molecules such as CD40, CD80 and CD86
leading to optimal APC- T-cell interaction and subsequent T-cell activation.