What’s the link between the immune system and aging? What specifically happens to your body when the immune system begins to fail?
Your immune system is a network in your body that protects you from infection. But it’s also a system that becomes less functional as you age, leading to a variety of harmful repercussions.
Let’s look at how a decline in your immune system’s functionality causes aging and how to fix it.
Your Immune System Becomes Less Capable
In Ageless, Andrew Steele explains that this decline affects many components of your immune system, and aging is sped up.
1) Your thymus deteriorates. Your thymus is an organ that produces T cells, the white blood cells you need to fight infections. It begins to decline in volume and function when you’re a child and halves in size every 15 years.
The potential fix: Sterilization stops the thymus’s decline, but Steele points out that this isn’t a practical treatment. Growth hormones or gene therapy could rejuvenate the thymus, and scientists think it might be possible to use stem cells to grow a new thymus.
2) Cells that remember past infections impair your body’s ability to fight new infections. Steele explains that memory T cells and B cells become specialized to an infection. These cells—such as the ones specialized to fighting a common virus called cytomegalovirus (CMV)—remain in your immune system for years afterward. As you age, you have fewer T cells that aren’t specialized. The ones that are specialized use up resources and cause your immune system to fixate on old infections, making it less effective against new ones.
The potential fix: Steele writes that scientists could eliminate these single-minded cells via processes that kill senescent cells. Other ideas include targeting cells that have DNA damage or extending the telomeres of aging memory T cells and B cells.
3) Your immune system gets less efficient at finding and destroying tumors, which is why cancer is more prevalent in older people.
The potential fix: Steele explains that an HSC transplant could reboot your entire immune system and boost its performance at destroying cancerous cells—but wiping out and restarting the immune system poses a lot of risks.
| Mustering (and Culling) the Forces You can think of your immune system as your body’s military force, as T. Colin Campbell and Thomas M. Campbell explain in The China Study. White blood cells, like the T cells and B cells Steele mentions, attack invading bacteria and viruses. The thymus starts training T cells before you’re born and produces all of your T cells by the time you reach puberty. Then it declines and is replaced by fat—but some experts think that growth hormones can turn it back into a functional gland. One expert has even injected himself to test the idea, but it’s not proven that the process regenerates the thymus or kickstarts T cell production, expanding your defensive force. If your T cells are limited in number, then why does Steele suggest killing some of them off? One reason is that when your T cells become specialized to fight off an invader like CMV, they leave your immune system with fewer unspecialized cells to fight other invaders. Worse, the T cells that remain look like senescent cells, with shortened telomeres and DNA damage. Experts contend that removing these cells might be best. But when it comes to CMV, experts don’t all agree that specialized T cells hurt you. In fact, there’s some evidence that CMV might strengthen your immune system by prompting it to send a more diverse population of T cells to fight a new infection. Dysfunctional T cells might also be the reason the immune system sometimes fails to find tumors, which Steele notes happens more often with age. (T cells latch onto protein fragments called neoantigens on the surface of a cancer cell as they pass by. But T cells are only good at recognizing neoantigens if they’re densely concentrated, so they don’t detect a tumor if only a few of its cells have a suspicious neoantigen.) Other experts agree with Steele that a bone marrow transplant could reboot the immune system. But this isn’t a procedure that patients undertake lightly: They often have to spend several weeks in the hospital, and they’re highly susceptible to infection right afterward and remain at elevated risk for a year or more. |
