Toll-like receptors (TLRs) are a type of protein found on the surface of certain immune cells. They play a crucial role in the body's defense system by recognizing pathogens like bacteria and viruses. When TLRs detect these harmful invaders, they trigger an immune response, helping the body to fight off infections. There are several types of TLRs, each specialized to identify different components of pathogens. For example, some TLRs recognize lipopolysaccharides from bacterial cell walls, while others detect viral RNA. This ability to sense a wide range of threats makes TLRs essential for maintaining immune health.