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.