The discovery of Toll-like receptors (TLRs) initiated a renaissance for the field of innate
immunity, leading to the discovery of multiple receptors and signalling pathways important
for host defence. TLRs are expressed highly on cells of the immune system and play a cru￾cial role in initiating an effective immune response that protects the host against invading
pathogens. Ten TLRs have been identified to date in humans. They recognised so-called
pathogen-associated molecular patterns (PAMPs) found within micro-organisms such as bac￾teria, viruses, and fungi (1). Association of PAMPs with a specific TLR results in receptor
dimerisation and activation of intra-cellular signalling cascades, leading to the expression of
cytokines, chemokines, and interferons required to activate effector mechanisms both innate
and adaptive, which lead to the elimination of the invading pathogen (2)