oihmclinic:
Simply put, your immune system's mission is to protect your body from disease and illness. The complex system is made up of cells in your skin, blood, bone marrow, tissues, and organs that, when functioning properly, should defend your body from potentially harmful pathogens (such as bacteria and viruses) while also limiting damage from noninfectious agents (like sunburn or cancer)
Every component of your immune system must function perfectly in order to protect your body from damage. The best way to ensure that happens is to engage in the good-for-you actions that your immune system relies on every day.

Here are six key ones.

1. Eat a Healthy Diet
According to Yufang Lin, MD, an integrative medicine doctor at Cleveland Clinic in Ohio, the nutrients you obtain from diet — particularly plant-based foods like fruits, vegetables, herbs, and spices — are critical to keeping your immune system functioning properly. "Many plant-based foods also include antiviral and antibacterial qualities that aid in the battle against infection,"
Protein is also necessary for immune system function. Protein's amino acids aid in the formation and maintenance of immune cells, therefore cutting back on this macronutrient may reduce your body's ability to fight infections.

2. Keep Stress Under Control
According to a review published in the October 2015 issue of Current Opinion in Psychology,
Chronically increased levels of the steroid hormone cortisol are a result of long-term stress. During short-term episodes of stress (when your body goes into "fight-or-flight" mode), the body relies on hormones like cortisol; cortisol has the good effect of stopping the immune system from responding before the stressful event is over (so your body can react to the immediate stressor). When cortisol levels are consistently high, however, the immune system is unable to go into gear and protect the body against pathogens such as viruses and bacteria.

3. Get Plenty of Good Quality Sleep
According to Lin, adequate sleep is critical for a healthy immune response because your body heals and regenerates while you sleep.
When you don't get enough sleep, your immune system may not be able to do these things as well, making it less able to defend your body against harmful invaders and increasing your chances of getting sick. One study published in the July–August 2017 issue of Behavioral Sleep Medicine found that compared with healthy young adults who did not have sleep problems, otherwise healthy young adults with insomnia were more susceptible to the flu even after getting vaccinated.
Sleep deprivation also raises cortisol levels, which is bad for immune function, according to Lin. "As a result, our immune system wears down, and we tend to have [fewer] reserves to fight off or recover from illness."

4. Exercise Regularly
Regular exercise lowers your risk of developing chronic diseases as well as viral and bacterial infections, according to a review in Frontiers in Immunology in April 2018.
Exercise also increases the release of endorphins (a group of hormones that reduce pain and induce feelings of pleasure), making it an excellent stress-reduction tool. "Because stress has a negative impact on our immune system, this is another way that exercise can improve immune response,"
Exercise may make your immune system more vigilant by distributing immune cells throughout your body to look for damaged or infected cells, according to studies on how exercise affects the body on a cellular level.
Sunshine also increases vitamin D levels in the body, which is important for immune health.

5. Don’t Smoke Cigarettes
Like alcohol, cigarette smoking can also affect immune health. “Anything that’s a toxin can compromise your immune system,” Kaplan says.
In particular, the chemicals released by cigarette smoke; carbon monoxide, nicotine, nitrogen oxides, and cadmium can interfere with growth and function of immune cells, like cytokines, T cells, and B cells, according to a November 2016 review in Oncotarget.
Smoking also worsens viral and bacterial infections (especially those of the lungs, like pneumonia, flu, and tuberculosis), post-surgical infections, and rheumatoid arthritis (an autoimmune disease in which the immune system attacks the joints), according to the CDC.
“Don’t smoke,” Lin says. And avoid secondhand smoke whenever possible.

6. Keep Symptoms of Chronic Conditions Under Control
Chronic conditions like asthma, heart disease, and diabetes can affect the immune system and increase risk of infections.
For example, when people with type 2 diabetes don’t manage their blood sugar properly, this can create a chronic, low-grade inflammatory response that weakens the body’s defense system, according to an October 2019 review in Current Diabetes Reviews.
Living with a chronic condition can be like trying to drive a car that has only three tires, Kaplan says. “If you get sick with a virus, it’s going to take more effort for your body to recover,” he explains.

If you manage your chronic conditions better, you'll free up more reserves to help your body fight infection. So make sure to keep up with medications, doctor visits, and healthy habits that help you manage your symptoms.

Your immune system will be grateful.