For more than 500 years, medical practitioners have tried to defeat infectious diseases by taking advantage of the body's ability to defend itself. Over the past several decades, however, the body's innate immune system -- the one we are born with -- has emerged as a new potential front line in battling a variety of diseases. The innate immune system, which provides the body's first, generalized response to infectious invasion, has the potential to be leveraged to activate responses to bacteria, viruses, and parasites and to provide possibilities for stimulating immune responses to tumor cells. Harnessing this inherent safeguard could provide important keys to understanding and treating a myriad of human diseases ranging from infectious and autoimmune diseases to cancer.