TLRs are believed to function as dimers. Though most TLRs appear to function as homodimers, TLR2 forms heterodimers with TLR1 or TLR6, each dimer having a different ligand specificity.  TLRs may also depend on other co-receptors for full ligand sensitivity, such as in the case of TLR4's recognition of LPS, which requires MD-2. CD14 and LPS-Binding Protein (LBP) are known to facilitate the presentation of LPS to MD-2.
A set of endosomal TLRs comprising TLR3, TLR7, TLR8 and TLR9 recognize nucleic acid derived from viruses as well as endogenous nucleic acids in context of pathogenic events. Activation of these receptor leads to production of inflammatory cytokines as well as type I interferons (interferon type I) to help fight viral infection.
The adapter proteins and kinases that mediate TLR signaling have also been targeted.  In addition, random germline mutagenesis with ENU has been used to decipher the TLR signaling pathways.  When activated, TLRs recruit adapter molecules within the cytoplasm of cells to propagate a signal.  Four adapter molecules are known to be involved in signaling.  These proteins are known as MyD88, TIRAP (also called Mal), TRIF, and TRAM (TRIF-related adaptor molecule).
TLR signaling is divided into two distinct signaling pathways, the MyD88-dependent and TRIF-dependent pathway.