Toll-like receptors (TLRs) constitute a huge family of Pattern Recognition Receptors (PRRs) which are involved in the innate and adaptive immune systems. TLR1-9 are recognized in both the human and mouse, while the TLR10 is specific to humans and TLR11-13 are detected in mice. The TLRs are recognized in different structures, tissues, and organs and their ligands are divided into external and internal subsets. TLRs encompass their signalling pathways and this characteristic makes them important in many different fields including microbial infectious diseases, auto-immune diseases, and cancers. The external ligands of pathogen-associated molecular patterns (PAMPs) and internal ligands of damage-associated molecular patterns (DAMPs) activate the TLRs and the related signalling pathways, inducing a cascade of changes.

TLRs are involved in different structures and they recruit different cells and mechanisms to dominate foreign pathogens, endogenous molecules, or malignancies. However, the TLRs may act as a double-edged sword; they have positive and negative roles in human health and illness. The innate and adaptive immune cells as well as non-immune system cells cooperate with TLRs and act as an organized harmonic orchestra. Interleukins, cytokines, and chemokines (including pro-inflammatory ones), cell proliferation, apoptosis, repair, and reconstruction mechanisms are supported by TLRs. Hence, they can be recognized as pivotal molecules in different diseases and cancers as well as in therapeutic strategies.

The aim of this Special Issue is to discuss all TLR signalling pathways, mechanisms, cells, and molecules which contribute to health, infectious diseases, autoimmune diseases, cancers, and even candidates for therapeutic strategies. Original research and review articles are welcome.

Potential topics include but are not limited to the following:

• Molecular biology of TLRs
• TLRs signalling pathways
• TLRs and mechanisms
• TLRs and mutations
• TLRs and health
• TLRs and infectious diseases
• TLRs and autoimmune diseases
• TLRs and therapeutic strategies
• TLRs and agonists