The immune system operates symbiotically with many other processes in the human body. As the first line of defense against pathogens and illness, it needs to be able to do its job properly if any foreign invaders manage to infiltrate the body.
When one factor of overall health is compromised, the immune system can falter, thus leaving you more susceptible to getting sick. But what factors influence the immune system, and how do they do so?
Let’s take a look at six major factors that influence immune function: age, diet, sleep, stress, environmental factors, and genetics.
1. How does age affect immunity?
The immune system is always adapting and changing. Children’s immune systems are just beginning to develop and recognize pathogens. This is why infants are much more likely to suffer grave consequences if they fall ill with an infection that an otherwise healthy child or adult could fight off easily. As babies become children, their immune systems begin to rely on both innate and acquired immunity – that is, the immune response they’re born with and the one that develops over time, respectively.
These immune systems work together to help ward off disease and illness, but as a person ages, the immune system changes too. When adults start to reach a certain age, usually in their 60s, their immune systems become less able to ward off pathogens, even if the body has encountered them before. This is because the body produces less and less of those all-important immune cells known as B and T cells. However, it is not fully understood how age leads to a reduced quality of specific immune cells.

2. How does diet affect immunity?
Nutrition has the ability to make or break overall health. What you put into your body matters more than many people believe. On a cellular level, every nutrient and macronutrient is required by the body for processes to run smoothly. Antioxidants, for example, are required to ward off oxidative stress. B vitamins lend a hand in energy levels, and a plethora of other vitamins are critical when it comes to immune health.
Vitamins such as C and D and minerals such as zinc, selenium, and iron are all important for overall immune health. This is because these nutrients help to grow immune cells as well as keeping them functioning as they should. When the body is depleted of these minerals and vitamins, the immune system doesn’t respond as well as it should because it doesn’t have the proper tools to do so.
3. How does sleep affect the immune system?
Sleep is a vital component to overall health. During sleep, the body rests, restores, and rejuvenates itself. Every person needs sleep to function, and chronic sleep deprivation can lead to a host of different health issues. When it comes to the immune system, sleep is just as vital as any other major factor.
While you’re sleeping, the immune system releases small proteins known as cytokines that play a vital role in cell signaling. When this happens, the cytokines can increase mild inflammation, which is designed to combat any illnesses. If you don’t get enough sleep, the production of the cytokines designed to protect you may decrease, leaving you more susceptible to disease. A lack of cytokines can also lead to a lack of antibodies, the immune cells designed to fight off specific antigens.
4. How does stress influence your immune system?
Stress is a dangerous health issue. Chronic stress can lead to a variety of different problems in all areas of the body, including the digestive system, the heart, and the brain. When it comes to the immune system, dealing with too much stress over a long period of time can make it less able to fight off disease.
Elevated levels of stress over extended periods can suppress your immune system because of the hormone cortisol. When cortisol is released into the blood, it can lower inflammation. It does this to help the body in periods of short-term stress. When the body gets used to that cortisol, though, the immune system suffers. This is because it becomes resistant to elevated levels of the hormone, and increases production of inflammatory cytokines that can lead to worsened immune function.
5. How do environmental factors affect the immune system?
The environment is full of bacteria and viruses that can infiltrate your body and make you sick. Other environmental factors, such as air pollution, can also have a negative impact on how well your immune system functions. If air pollution particles make their way into the body, they can trigger an immune response that causes inflammation. This could lead to changes in how the immune system functions.
Other environmental factors that play a role in how well the immune system works include sun exposure, how much you exercise, and exposure to harmful substances in the air, water, soil, or food. When certain toxins begin to build up in the body, the immune function suffers.

6. How do genetic factors affect the immune system?
Close to 75% of a person’s immunity can be influenced by their genetic makeup. It was previously thought that only the innate immune system was heavily influenced by genetics; however, researchers are now realizing that even the adaptive immune system is developed based on variations in a person’s specific genome.
Some major factors affecting how well your immune system works are hard to change, such as genetics and age. However, diet, sleep, stress, and environment can all be managed to help monitor and even improve your immune health.