Toll-like receptors (TLRs) belong to a class of pattern recognition receptors (PRRs) that constitute the first line of defense system against pathogenic microbes. TLRs recognize both the external pathogen-associated molecular patterns (PAMPs) derived from various microbes and endogenous self-derived molecules from damaged cells, damage-associated molecular patterns (DAMPs). TLRs play a crucial role in innate immunity by initiating signal transduction pathways, leading to activation of the transcription factors NF-kB and IRFs and expression of cytokines, chemokines, and type I IFNs genes. TLRs comprise a family of type I transmembrane receptors that contain three structural domains: an extracellular LRR (Leucine-Rich Repeat) domain, a transmembrane domain and an intracellular Toll/IL-1 receptor (TIR) domain. TLRs are expressed in both innate immune cells like macrophages and dendritic cells, and in non-immune cells including fibroblast cells and epithelial cells. In humans, 10 TLRs have been identified (TLR1–TLR10) in comparison to mouse where 13 TLRs (TLR1–TLR13) have been identified till now.
Abeomics have developed several TLR antibodies including antibodies to TLR6, TLR9, TLR3, TLR4, TLR8, TLR5, and other proteins of TLR pathways.