 They are part of a family of "pattern recognition" receptors that detect pathogens immediately, even those the body has not yet encountered, long before adaptive immunity can intervene against foreign invaders.These receptors are critical to the first line of immunological defense against a broad range of pathogens, including otherwise lethal viruses and various forms of cancer.When, for example, double-stranded RNA molecules from an RNA viral infection bind to TLR-3 receptors, the virus in this way inactivates the innate immune system, rendering it unable to signal the rest of the body's defenses.