The Stats


   1% of cells in your body are white blood cells 

   80% of your immune system resides in your gut

   78% of individuals have an autoimmune disorder who are women


It’s called the immune system because it’s not just one cell type or one organ. Your immune system is a complex and dynamic network of cells, pathways, organs, tissues, and organisms that work in harmony to synthesize information needed to respond – both proactively and reactively – to perceived foreign invaders in your body and your immediate environment. It is so complex that at any given moment your immune system can become activated, heightened, or weakened.

What can you do to support your immune system? Although it is not completely understood, there are things you can do that will influence how well your immune system works.

Immune system inner-workings: the very basics

The primary function of your immune system is to equip your body with the capacity to recognize materials that are foreign to you and to neutralize, eliminate, engulf, or kill them, hopefully without any injury to you. Foreign particles can be bacteria, viruses, parasites, fungi, and even food that is absorbed without being properly digested (the genesis of food allergies). The ability to differentiate “self” from “foreign” is the crux of its job.

Your skin and the mucous membranes in your mouth, nose, and GI tract are the first lines of natural defense, and natural substances secreted in your sweat and saliva are detrimental to the growth of foreign microorganisms. Three examples: your skin and stomach have a naturally acidic level that inhibits bacterial growth; enzymatic lysosomes in your tears and saliva break down bacterial cell walls; and your sweat contains glycoproteins that adhere to microbes to trap and “wash” them away.

If foreign particles make it through these natural ports of entry into the blood or lymph, then they can initiate an immune response depending on your immune tolerance. Your innate immune system reacts first and provides a fixed response to these substances it encounters. This can include developing a fever or secreting a variety of enzymes and proteins intended to kill pathogenic microorganisms. The pathways that complement these processes trigger a natural inflammatory response that facilitates the movement of necessary immune system components to the site of infection or damage. In addition to the various types of white blood cells – monocytes, lymphocytes, macrophages, eosinophils, basophils, and neutrophils – dozens of proteins, cytokines, and other substances in this complex response are activated in different locations, all with the same goal – to kill invaders.

Although it’s different, but not entirely separate from your innate immune system, you also have an adaptive immune response that provides a complex set of genetically controlled, interdependent, and interactive responses to foreign substances. Your adaptive immune system is comprised of a relatively small number of cells that have the capacity to recognize certain foreign substances. The different types of cells of the adaptive immune system – B-cells and T-cells – work synergistically with the innate immune system to recognize foreign substances (usually bacteria and viruses) and produce antibodies against these foreign substances that eventually kill them. And although this might sound relatively simple, this intricate process also requires the assistance of many other essential and complex steps for it to function properly.

One unique aspect about the adaptive immune response is that it can produce large quantities of long-lived cells (i.e., memory cells) that live dormant but can be quickly re-expressed during subsequent encounters with the same foreign substance. For example, your adaptive immune response is what triggers an allergic reaction or rejects transplanted tissue.

GI tract and the immune system

Although much immune activity goes on in your blood, the important role that your gut plays in your immune system can’t be overlooked. Although you encounter bacteria in the air, on objects you touch, and naturally on your skin, the most bacteria you are exposed to reside in your gut. The mix of these bacteria, both good and bad, plays a huge role not only in your digestive system but also in your immune system. In fact, it is estimated that 80 percent of your immune system might be located in your gut.

The protective lining in your gut, which includes epithelial cells and its mucosal lining, acts as a physical barrier to foreign invaders to your bloodstream, assisted by the principal immune-protective antibody, secretory immunoglobulin A (sIgA). Compromises in gut integrity, which can occur from nutrient deficiencies, free radical damage, antibiotic use, and inflammation, can allow more “bad” bacteria into your bloodstream. Acting in concert, the beneficial gut bacteria also play a major role in preventing pathogens from being absorbed.

Things you do every day can affect your immune system

Stress negatively impacts the immune system.

Over-production of the stress hormone, cortisol, can weaken the immune system. In situations of chronic stress, cortisol perpetuates the production of pro-inflammatory cytokines1 and reduces the production of white blood cells and natural killer cells, which ultimately disrupts the immune system and the impact it can exert on foreign particles.

Negative thoughts can even impact the immune system.

The good news is that happiness and a positive mood can support your immune system. Research has shown that pleasant emotions can increase sIgA while decreasing cortisol. There is also data to support the hypothesis that individuals who have a naturally negative outlook might be at greater risk for illness than individuals who have a naturally positive outlook.2

Sleep deprivation can disrupt immune function.

In normal sleep-wake cycles, T-cells and the production of pro-inflammatory cytokines tend to peak during early nighttime sleep, whereas other immune cells, like cytotoxic natural killer cells and anti-inflammatory cytokines, reach peak levels during daytime wakefulness. With sleep deprivation, undesirable changes in T-cell function and cytokine activity can occur. Because sleep plays a specific role in the formation of the adaptive immune system, which is associated with different stages of sleep, disrupted sleep patterns can adversely influence immune function.3

Keep it clean, but not antiseptic.

It is good practice to engage in good hand-washing hygiene to avoid the direct spread of bacteria and viruses. However, the overuse of antibacterial soaps and antibiotics should be avoided because they can’t differentiate between good and bad bacteria and therefore kill both. Maintaining an optimal balance of good-to-bad bacteria on your skin and in your gut promotes optimal immune function. Similarly, short exposures to foreign substances help support a healthy immune response.


  1. Morey J, Boggero I, Scott A, Segerstrom S. Current directions in stress and human immune function. Curr Opin Psychol 2015;5:13-17.

  2. Barak Y. The immune system and happiness. Autoimmun Rev 2006;5(8):523-527.

  3. Besedovsky L, Lange T, Born J. Sleep and immune function. Pflugers Arch 2012;463(1):121-137.