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How Your Immune System Works After You Turn 50

Understanding your body's defenses against coronavirus, flu and the common cold

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En español | It's nearly impossible to find the good in a global pandemic, but COVID-19 did deliver one important lesson each of us should acknowledge: Our immune systems are in trouble. They're not “weaker” than those of generations ago. But they are more “dysregulated” — the medical term for a biological process or function that isn't working the way it should. Your immune system is less able to tell a deadly invader from a harmless one, for example, and more likely than in the past to attack your body's own healthy tissue by mistake. Plus, it's constantly turned on and working in counterproductive ways that were once much less common. Each of these is an indicator of disturbed immune function, and together they use up resources that should be going elsewhere.

“We absolutely have more dysregulation in our population today,” says Mark Ansel, a professor of microbiology and immunology at the University of California, San Francisco. “And it's related to the changing way that we interact with our environment — everything from what we eat to what we do.” That's disturbing news for all of us as we head into the teeth of this winter's perfect storm: a potentially resurgent novel coronavirus that's still wreaking havoc across the nation, and the opening months of our annual flu season. But we're not helpless — not by a long shot — and here's what you need to know.


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How the immune system misfires

There are many ways in which our bodies manifest immune problems, but three of them stand out, and the prevalence of each is increasing throughout our population.

Chronic inflammation. Among those who were hospitalized with COVID-19, 34 percent had diabetes, 42 percent were obese and 57 percent had high blood pressure, according to a study published in JAMA in April. A common factor for all three conditions is chronic inflammation. It causes your immune system to pump out white blood cells and chemical messengers that keep your defenses actively engaged 24/7.

"It's almost like you're using all the immune system's resources just to keep this fire smoldering,” says Helen Messier, a California-based immunologist and director at Altum Medical. “When a viral infection happens during chronic inflammation, the immune system may either not be able to mount an appropriate immune response or, in the case of COVID-19, it doesn't have a good response initially but then tries to overcome it; the underlying inflammation can lead to an overpowering response, or ‘cytokine storm.’ "

Autoimmune diseases. Researchers have identified more than 80 distinct autoimmune disorders. While a few are widely known — such as rheumatoid arthritis (RA), lupus and type 1 diabetes — many defy classification. But all share the common underlying issue of the body's immune system attacking itself.


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More than 24 million Americans have an autoimmune disease, and that number is climbing. When researchers in North Carolina examined 14,000 Americans between 1991 and 2012, they discovered that the prevalence of antinuclear antibodies, an early marker of autoimmunity, had increased by 45 percent. Another study — this one spanning three decades — found that autoimmune diseases of the joints, glands and digestive system are rising at a steady 3.7 to 7.1 percent each year. Smoking and being overweight are two risk factors within your control that are associated with greater risk of RA, one of the most common autoimmune disorders, which affects the lining of your joints.

Food allergies. This is an immune system overreaction that can occur immediately after eating something as seemingly benign as a peanut butter and jelly sandwich. Food allergies now afflict more than 1 in 10 adults, according to a Northwestern University study of 40,000 people. Rates are particularly high for shellfish, milk and nut allergies, and the number of people who have them has been climbing steadily since the 1980s. “We're now more susceptible to responses against harmless stuff that shouldn't be a big problem for our immune system,” Ansel says. “But instead we generate these big and often destructive responses.”

So what's causing the confusion in the immune system? To a large extent, it's our changing environment.

"Our bodies deal with thousands of chemicals that were not in the environment 50 years ago — and some not even 20 years ago,” says Aristo Vojdani, a clinical immunologist and adjunct associate professor in the Department of Preventive Medicine at Loma Linda University. Heavy metals and industrial pollutants are among the top offenders, but pesticides, preservatives and compounds in food can also alter immune function. All told, the Centers for Disease Control and Prevention (CDC) counts more than 300 environmental chemicals that reach measurable levels in our bodies.

"Exposure to different environmental insults can add up and alter how the immune system functions,” says David Shepherd, a professor of environmental immunology at the University of Montana. “In some cases, [the chemicals] are immune-activating,” meaning they cause inflammation, “and in others, they're immunosuppressive,” which makes you susceptible to attack.

Add to that a general decrease in physical exercise, ever-increasing levels of stress and, yes, our increasing age. All these many factors have laid siege to our immune system like never before.

We have the power

The older we get, the more dysregulation our immune systems experience. Eight out of 10 COVID-19-related deaths reported in the United States have occurred among adults 65 and older, according to the CDC. And during the 2018–2019 season, influenza was linked to nearly 280,000 hospitalizations and more than 25,000 deaths in that same age group.

But hidden in these figures is a bit of good news: The number of candles on your cake is just one factor in your immune system's biological age. “Only a small percentage — let's say 10 percent — of the decline in immunity is caused by aging itself,” Vojdani says.

Genetics plays a role as well, but much less than you'd think. A few years ago, an international team of researchers collected blood from 210 sets of twins ranging in age from 8 to 82, and surveyed the samples for white blood cells and other markers of immune strength. The researchers concluded that 58 percent of the immune system is almost completely determined by nongenetic factors — factors that you can influence every day, and that can not only reduce your COVID-19 risk but also relieve you of the burden of so many other immune system–related diseases.

Inflammation hinders our body's fight against the coronavirus and flu.

"There are many older people who have stronger immune systems than some younger people,” Vojdani says. “The answer is really lifestyle.”

And those lifestyle choices are easy stuff, too. Start by eating unprocessed foods as much as possible — lean meats, fruits and vegetables, and whole grains that aren't prepackaged with preservatives, Vojdani says. It's equally important to avoid smoking and secondhand smoke, overconsumption of alcohol, fried foods and added sugars — and to ensure we're getting proper amounts of essential nutrients.

We can also take time each day to exercise and find ways to reduce our stress levels. According to a JAMA study, people who suffer from stress-related disorders are 36 percent more likely to develop an autoimmune disorder. And, not surprisingly, this past year has been particularly stressful. A survey by the American Psychological Association suggests that our stress levels have jumped 10 percent.

researcher looks at computer screen with images of viruses

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Get to know your immune system

When bacteria and viruses enter your body, these natural defenders spring into action   

Macrophage
This gargantuan white blood cell lies in wait within healthy tissue. Sometimes years pass without action, but when a pathogen emerges, macrophages release a blast of proteins called cytokines, which calls the immune system into battle. From there, the macrophage joins the cleanup crew by gobbling up dead and crippled pathogens.

Natural Killer Cell
Some infected cells can be rendered “invisible” to the immune system, which allows the pathogen to continue to spread unabated. That’s when natural killer cells provide an extra layer of defense. A natural killer cell has the ability to identify abnormal cellular appearance — as is often the case with cells infected by a virus. The killer cell studies its mark, and if the suspect cell appears to be infected, it releases proteins near the suspected pathogen. The pathogen then eats the protein — a fatal, final meal.

Neutrophil
At the first sign of trouble, neutrophils swarm like killer bees with multiple stingers. Neutrophils can capture their enemy, set traps, inject poison and amplify signals that pull in more immune-system warriors. Neutrophils only live for about a day, but as long as the battle continues, fresh cells keep showing up to fight. Unfortunately, in their frenzy, they can often mistake healthy cells for the enemy. When that happens, and the neutrophils attack healthy tissue, the result is inflammation, and inflammatory diseases, throughout the body.

B Cell
Although B cells don’t kill invaders directly, they help to slow down pathogens by covering them with sticky Y-shaped proteins, robbing them of their strength and making them easy targets for cells like macrophages, which eat them in clumps. The B cell is an adaptive immune cell, meaning it is highly effective against diseases it has battled before but struggles to recognize new pathogens. When a novel coronavirus arrives, it takes time to ramp up production of antibodies.

T Cell
The T cell is one of the special-ops white blood cells called upon to “recognize” a foreign invader and know exactly how to fight it off. With new enemies like COVID-19, however, the process can take weeks. Once the T cell learns the code — essentially mapping the molecular structure on a pathogen’s surface — it quickly trains an army of T cells to begin opening infected cells and pumping them full of toxins. Doctors call this process immunity, although with COVID-19, we still aren’t certain how long it lasts.

Clint Carter reports on wellness for Men's Health and other national magazines.

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