Alternative definition : KEGG: Specific families of pattern recognition receptors are responsible for detecting
microbial pathogens and generating innate immune responses. Toll-like receptors (TLRs)
are membrane-bound receptors identified as homologs of Toll in Drosophila. Mammalian
TLRs are expressed on innate immune cells, such as macrophages and dendritic cells,
and respond to the membrane components of Gram-positive or Gram-negative bacteria.
Pathogen recognition by TLRs provokes rapid activation of innate immunity by inducing
production of proinflammatory cytokines and upregulation of costimulatory molecules.
TLR signaling pathways are separated into two groups: a MyD88-dependent pathway that
leads to the production of proinflammatory cytokines with quick activation of NF-kappa
B and MAPK, and a MyD88-independent pathway associated with the induction of IFN-beta
and IFN-inducible genes, and maturation of dendritic cells with slow activation of
NF-kappa B and MAPK.;