Immunity refers to the human body's ability to resist harmful microorganisms.

Our immune system has three lines of defense and includes an extensive and complex network of organs, cells and circulating substances.

The first line of defense is the physical and chemical barrier such as skin, mucus membranes lining, the tissues that are exposed to air, gastric acid, digestive enzymes and gut microbiome.

The second line of defense is the human innate immunity, consisting of white blood cells or leukocytes.

The third line of defense is the adaptive immunity, which is responsible for more complex reactions. It consists of natural killer cells, T lymphocytes and B lymphocytes.

A robust, well balanced immune system protects us from infections. However, there are many factors that can disrupt the smooth functioning of our immune system and lead to an underactive (immunodeficiency) or overactive immune (autoimmunity) response.

The human immune system also changes with age. Immunoscenescens refers to the gradual deterioration of the immune system brought on by the aging process. This means that there are less effective innate and adaptive immune responses and increased susceptibility to infections, cancer, chronic inflammatory disorders and autoimmune diseases (Pamela W. Smith, MD. Max Your Immunity, 2021).

Laboratory studies are helpful in monitoring how the immune system functions.

Gut microbiom testing can assess gastrointestinal health and reveal important information about the root causes of many conditions including autoimmune diseases.

The laboratory evaluation of the innate immune system includes a complete blood count (CBC) with differential.

To measure the adaptive immune system many advanced tests are available such as the measurement of antibody levels and function, flow cytometry, cytokine assays and genetic assays.

Clinical studies suggest that an unhealthy lifestyle is associated with a compromised immune system. Therefore, the key strategies that can help improve and balance the immune function include lifestyle modifications ( alcohol use moderation,  quitting smoking, stress management, good sleep, healthy diet and consistent exercise), the treatment of comorbid conditions, restoring gut health, and herbal and nutritional therapies.