You probably know what the immune system is in a general sense. It’s your body’s great defender, fighting off illness and disease. You probably also know that it changes throughout your life. That’s where it starts getting interesting.
Babies, when they’re first born, don’t have much in the way of immunity. Their bodies need to learn to fight off even everyday germs. Then we (hopefully) grow into healthy adulthood, before the immune system starts to weaken and fade again in old age. The elderly are much more at risk from a whole range of diseases, and that has a big impact on human longevity.
What you might not realize is that immunity actually comes in different forms. There’s innate immunity, the kind that’s inherent from birth, and there’s adaptive immunity, also called acquired immunity. That’s the sort that we pick up as we go, our bodies learning how to deal with new pathogens every time they encounter them.
Innate immunity is your body’s first line of defense, the immediate reaction when it’s being invaded. That means it’s pretty general. It can cover most common illnesses and injuries with some success, like when a cut becomes inflamed, but it can’t target the trickier pathogens that require a more specific approach. For these, you need to either catch the disease itself or receive a vaccination to teach your body how to respond.
Now research is underway into the specifics of how the different kinds of immunity connect to our longevity (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7673842/). We know that the immune system can become less effective as we age, and both types of immunity seem to change as we grow older. If we want to improve longevity, we need to understand how and why.
For older people, their immune systems are less able to learn and adapt when they encounter new diseases. Meanwhile, even simple injuries can have a more enduring impact, with inflammation lasting much longer and causing low-level but ongoing problems. The systems involved in these immune reactions are complicated, and we’re only just beginning to understand how they all fit together.
Aging is complicated. The immune system is complicated. Both of those things together may hold important insights into longevity, but first we have to investigate how they work and their relationship. That also means exploring the difference between innate and adaptive immunity.
