Tripping the Innate Immune Response

Join Our Community of Science Lovers!

On supporting science journalism

If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.

When a bacterium enters the body, the first line of defense it encounters is the innate immune system. This rapid-response system recognizes common bacterial components such as lipoproteins, lipocarbohydrates or bacterial DNA, and sets off a chain of reactions to kill the invader and alert the adaptive immune system, which can offer a more targeted attack, if needed. Now researchers from Japan and Germany have found a specific receptor protein, called Toll-like receptor 9, that the innate immune system requires for the recognition of bacterial DNA. They report their findings in today's Nature.

Unlike the DNA of body cells, DNA from bacteria frequently contains a motif of two particular bases, C and G in its unmethylated form. The scientists bred mice that lack Toll-like receptor 9 and found that these animals, unlike their wildtype cousins, no longer showed any innate immune response to CG-containing DNA. Furthermore, these mice did not die from the shock that CG-containing DNA can induce in normal mice. Understanding the exact mechanism of how bacterial DNA stimulates the innate immune system can possibly help scientists improve the effects of DNA vaccines, which work by getting the immune system's attention.

Subscribe to Support Independent Journalism

Great science journalism requires human expertise, time, effort and creativity. And it costs money. That’s why I and the journalists here at Scientific American hope you’ll join our community.

When you subscribe, you are supporting staff and freelance journalists who are passionate about telling science stories that are true, important and compelling. Our editors and reporters are often experts in their fields, which means they understand the nuances of big discoveries and can untangle the breakthroughs from the hype. With a subscription, you are also supporting rigorous fact-checking to ensure the words we publish are precise and accurate. And you’re supporting original illustrations, graphics and photos that bring you closer to an advanced laboratory, an ice sheet in Antarctica or a space mission in orbit. You’re helping us craft other types of high-quality journalism as well: Our newsletters are carefully written, edited and curated by staffers you have or will come to know and love. Our Science Quickly podcast is based on original reporting, collaboration with editors and scientists and exacting production.

Subscriptions keep this engine running so we can continue to deliver thoughtful, rigorous and independent science journalism to you. In an era of viral misinformation, this work is crucial. If you value what we do, I hope you’ll consider joining us as a subscriber

Thank you,

Jeanna Bryner, Editor in Chief, Scientific American