What is immunity?
Immunity is our body’s ability to recognise external invaders such as bacteria, viruses, fungi, and toxins (chemicals produced by microbes) and neutralise them to prevent the diseases they cause.
Types of immunity
Our immune system has two components:
- Innate immunity
- Adaptive or acquired immunity, which in turn is divided into:
- Active immunity, which develops in response to infection or vaccination:
- Natural immunity – antibodies developed in response to the infection.
- Artificial immunity – antibodies developed in response to a vaccine.
- Passive immunity, which develops after you have received antibodies from another person or somewhere else:
- Natural immunity – antibodies are received from the mother, for example through the placenta or with breast milk.
- Artificial immunity – antibodies are obtained from a medicine, such as an injection or infusion of gamma globulin (immunoglobulin).
- Active immunity, which develops in response to infection or vaccination:
Innate immunity (also called non-specific, generic or natural immunity) is the body’s primary defence system that we are born with. It is unrelated to previous infections and immunisations (vaccinations).
Innate immunity is not targeted against a specific pathogen but protects us against a wide range of potential pathogens.
Innate immunity is very stable, but individuals may have different resistance to the same disease (individual differences in immunity).
Innate or non-specific immunity can be thought of as four types of protective barriers:
- Anatomical and physical barriers (e.g., skin, mucous membranes).
- Physiological and chemical barriers (e.g., body temperature, low pH and chemical mediators such as fever, breast milk, gastric juice, saliva, etc.).
- Biological barriers (e.g., Endocytosis, Phagocytosis).
- General barriers that could be related to age, race or individual immunity.
Adaptive or acquired immunity
Adaptive immunity, also called acquired or specific immunity, is a complex and highly specialised defence system that the body develops in response to exposure to specific pathogens or antigens. It is characterised by the ability to adapt to and remember past exposure to specific pathogens and to provide a reinforced and targeted response when exposed to them again.
In particular, adaptive immunity is designed to distinguish “own” from ” strangers” (cells/substances with foreign genetic information – microorganisms, toxins, tumour cells, transplants, etc.) and neutralise these “strangers”.
Adaptive immunity has two main components:
- Humoral immunity. B lymphocytes (or B cells) produce antibodies (immunoglobulins). These antibodies circulate in the blood and lymphatic system, recognise antigens (molecules or molecular structures that the immune system recognises as strangers) and neutralise or mark them for destruction by other immune cells.
- Cell-mediated immunity. Unlike humoral immunity, which is based on antibodies produced by B cells, cell-mediated immunity focuses on the direct action of T lymphocytes (or T cells) to directly attack and destroy infected or abnormal cells. Cell-mediated immunity is particularly important for protection against intracellular pathogens (e.g. viruses) and for destroying cancer cells.
How does immunity work?
Immunity is a complex system of inter-coordinated defence mechanisms that works roughly like this:
- Innate immunity (the first line of defence) – the aim is to prevent pathogens (bacteria, viruses, fungi or parasites that can cause disease) from entering the body:
- Physical barriers (skin and mucous membranes, etc.).
- Chemical barriers (stomach acid, enzymes, etc.).
- Innate immunity (second line of defence):
- Inflammatory reactions. When pathogens overcome physical and chemical barriers, an inflammatory reaction starts in the body – white blood cells (especially neutrophils and macrophages) are directed to the point of infection to neutralise and destroy the pathogens.
- Complement system. Proteins in the blood enhance the immune response by promoting inflammation, directly attacking pathogens and promoting phagocytosis.
- Natural Killer (NK) Cells recognise and destroy infected or abnormal cells.
- Adaptive immunity (third line of defence):
- If the innate immune system is unable to counter a threat, the adaptive immune system is activated which already recognises specific pathogens or antigens;
- T cells identify antigens;
- T cells are activated, including helper T cells and cytotoxic T cells. Helper T cells stimulate B cells (humoral immunity) and cytotoxic T cells (cell-mediated immunity).
- Antibodies are formed (humoral immunity). B cells start to produce antibodies. Antibodies circulate in the blood and bind to pathogens neutralising them or marking them for destruction.
- Cytotoxic T cells directly attack and destroy infected cells (preventing the spread of infection).
- Long-term protection:
- Both B and T cells can “remember” specific pathogens. If the body is exposed to them again, the immune system can react more quickly and effectively.
- Vaccination artificially “creates memories” of a particular pathogen, thus boosting the body’s ability to recognise and respond more quickly to potential threats, even if the person has not previously contracted the disease.
Boosting immunity with dietary supplements
There are many dietary supplements that promise to boost immunity or improve the health of the immune system.
Although some supplements have been found to alter some parameters of the immune system, there is no evidence to date that they actually boost immunity in the sense of better protection against infections and diseases.
There is no evidence yet that any substance can improve immunity. For example, if studies show that a plant or substance might increase the level of antibodies in the blood – we don’t really know if this is actually beneficial for overall immunity, because the immune system is very complex. In other words, even if a particular substance does increase antibody levels, we don’t really know how it will affect the other components of the immune system.
How to boost your immune system?
What to do if supplements don’t help?
You know – nothing new here 😊.
Everything as usual – the best way to naturally keep your immune system working properly is to live a healthy lifestyle:
- A healthy diet – lots of fruit, vegetables, legumes, nuts, seeds and a minimum of ultra-processed foods. In other words, we provide the body with the vitamins and minerals it needs to keep the immune system working:
- Vitamin B6 – chicken, salmon, tuna, bananas, dark green leafy vegetables, potatoes (with peel), etc.
- Vitamin C – citrus fruits, strawberries, tomatoes, broccoli, spinach, etc.
- Vitamin E – almonds, sunflower and safflower oil, sunflower seeds, peanut butter, spinach, etc.
- Zinc – oysters, red meat, poultry, beans, dairy products, etc.
- Magnesium – whole wheat products, nuts, seeds, etc.
- Enough physical activity (e.g., at least 10,000 steps a day).
- Enough healthy sleep.
- Enough water.
- Stress management.
- Moderate alcohol consumption and avoidance of other unhealthy habits.
There are also some very interesting studies suggesting that we can, in fact, boost our immunity very effectively by increasing the level of Natural Killer (NK) Cells and – we can do it for free!
By taking a walk in the forest.
The forest air is very rich in phytoncides. Phytoncides are substances released by plants (e.g. herbs, garlic…) and especially by conifers.
Phytoncides have beneficial effects on our body – lowering cortisol levels, normalising the nervous system, lowering blood pressure…
In 2007, a study in Japan showed that being in the forest significantly increases the activity and the number of natural killer cells.
Young and healthy men aged 37-55 years walked in the forest for three days. On the first day for two hours in the afternoon, and on the second and third days for two hours in the morning and two hours in the afternoon.
Blood samples were taken before the study and on the second and third days of the study.
In almost all men, natural killer cell activity increased by about 50% on the third day (compared with the pre-study measurement).
Natural killer cell activity increased significantly both on day three and between days one and two.
Overall, this study shows that walking in the forest can increase the number and activity of natural killer cells.
A similar study was carried out in Taiwan in 2018 and showed similar results.
In other words, there is good reason to suppose that regular walks of at least two hours in a park or forest can significantly improve the number and activity of natural endothelial cells, which are essential for immunity.
Phytoncides are most concentrated in coniferous forests during the warm season, and as little as one day in the forest can have a beneficial effect on the immune system, lasting for about 7 days.
Increased temperature and inflammation are a reaction of our immune system helping to neutralise “invaders” – bacteria, viruses, fungi, toxins …
The best way to strengthen your immunity is to live a healthy lifestyle and eat a balanced diet.
Overmedication, not always thought through, can also cause immune system problems.
In other words, take care of yourself and then your immune system will take care of you.
Eat a balanced diet, exercise and – be healthy!
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