20 things to know about your immune system

Your immune system plays a vital role in keeping you healthy. A bit like a biological bodyguard who hunts down micro-organisms that could make you sick (viruses, bacteria, fungi, parasites, etc.), it protects you from disease and infection. Here are 20 things you might not know about the immune system.



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Innate immunity offers immediate protection

Innate immunity is one of your immune system’s two defence mechanisms. Your skin and mucous membranes act as internal and external defence barriers that stop infectious agents from entering and spreading throughout your body.



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Adaptive immunity remembers infectious agents

When a virus or bacterium manages to get past your innate immunity, your second line of defence, adaptive immunity, steps up.

After fighting an infectious agent, your immune system remembers the encounter (immunologic memory), enabling it to react more efficiently the next time you come into contact with that pathogen.

Thanks to this defence barrier, most people only have to contract a virus, such as chickenpox, once in a lifetime.



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Only vertebrates have adaptive immune systems

Not all species have an adaptive immune system. In fact, only jawed vertebrates, gnathostomes, have such a defence mechanism.

Gnathostomes include, among others, fish and tetrapods.



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Babies benefit temporarily from their mothers’ immune systems

During the last trimester, mothers transmit some of their antibodies to their babies through the placenta, providing newborns with better protection against infections from birth. The protection is temporary, though, diminishing after the first few weeks of life.

Premature babies do not benefit from such protection due to an interruption in the transfer of antibodies.



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Breast milk contains antibodies



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Immune system efficiency decreases with age

As you get older, your immune system becomes less efficient. Macrophages, for example, have more difficulty eliminating cancerous cells, explaining in part why cancer rates are higher among older people.



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Our immune system is shaped by our environment

While genes play a role in determining your immune system’s efficiency, researchers have discovered that it is shaped to a greater degree by your environment.

One study has shown that even twins have essentially different immune systems. In fact, as twins age, their immune systems diverge even further.

Why? Simply put, as they grow older, each twin is exposed to a different environment. Most don’t work in the same place or frequent the same public areas.



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Stress harms the immune system

Stress may be causing more than your insomnia. Chronic stress can also damage your immune system. People with elevated levels of the stress hormone cortisol run a higher risk of developing infections, like colds, because the cells of their immune systems are less responsive.



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You have billions of white blood cells

To protect you from infections, your immune system calls on its soldiers, white blood cells (leukocytes). An enormous number of white blood cells, anywhere from 7,000 to 10,000, are found in a single microlitre of blood. What’s more, you make about 100 billion new white blood cells each day.



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Too many white blood cells may indicate a problem

Having too many white blood cells (11,000 or more per microlitre) in your body is not necessarily good news. While certain medications increase white blood cell production, infections and some cancers can have the same effect.



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Fever and the immune system

In many cases, a fever is your immune system’s response to an infection, such as a virus or bacterium. A fever, however, is not an actual defence mechanism, but rather a sign that the immune system has been activated and is releasing white blood cells.



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Laughter is good for the immune system

Unlike stress, laughter has a positive effect on the immune system. When you laugh, antibody production increases, especially in your nose and respiratory passages. Laughing doesn’t immunize you against all infections, but rather improves your resistance to certain diseases and cancers.



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Allergies and the immune system

Everyone knows that itchy eyes, sneezing, and rashes are common allergy symptoms. Contrary to popular belief, allergies are not caused by a deficient immune system, but rather an immune system that overreacts to a harmless substance.



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Intestines play a vital role in your immune system

Intestinal flora plays an important role in your immune system. Researchers have discovered that people with deficient intestinal flora have fewer than average macrophages and monocytes, leaving them less able to fight off infections.



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Some children are born with an inefficient immune system

In the United States, approximately one in every 58,000 children are born with severe combined immunodeficiency (SCID). Their insufficient number of lymphocytes leaves their immune systems incapable of efficiently fighting infections like viruses, bacteria, and fungi.

Children suffering from this disease must be isolated to prevent them from contracting viruses.



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Lack of sleep harms your immune system

Sleep is closely linked to immune system health. According to a 2015 study, those who sleep fewer than six hours per night are four times more likely to develop an infection.



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Small doses of sunlight may be good for the immune system

One study has found that small quantities of sunlight is good for the immune system. Moderate exposure to UVB rays could increase your protection against infections and improve your skin’s defence system.

Be careful, though—getting too much sun increases your risk of developing skin cancer.



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Your immune system can turn against you

In some cases, the immune system can turn against the body. In effect, antibodies attack healthy cells.

This phenomenon is caused by an autoimmune disease. Type 1 diabetes and multiple sclerosis number among the nearly 100 such conditions.



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The immune system involves many organs

The immune system relies on several organs (lymphoid organs). Bone marrow and the thymus, for example, are responsible for producing lymphocytes.

The spleen, lymph nodes, and adenoids, through which immune cells circulate, also play an important role.



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Sports stimulate the immune system

Regular physical activity can help stimulate the immune system. To fully benefit from exercise, however, avoid going overboard. Intensive athletic activity may actually have an opposite effect. While excessive training dramatically increases your lymphocytes, their numbers drop shortly afterwards, increasing your risk of developing an infection.



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