We know our body is equipped to provide us immunity. But do we know, how does it provide immunity? Knowing this will help us support our body’s immune system naturally. What is immunity? In one of my LinkedIn article, immunity was specified as “the ability of a body to fight infection”. In general, immunity is “the state of not being affected by something, that are normally considered as harmful”. What is harmful and what is not, depends on our ability to deal with the so-called harmful thing. For example, dealing with a major fire in a building is harmful to a common man but is harmless for firefighters. Firefighters protect people and are not afraid to deal with the fire, because they have got appropriate knowledge, training, and experience plus they are equipped with adequate resources to deal with the fire. Similarly, in dealing with an infection, our body’s immune system is knowledgeable, trained, and possess vast experience in dealing with infection naturally. How can we say that? Because it is there in our DNA, the genetic (hereditary) material present in nearly every cell of our body.
First lines of defense
As mentioned earlier, immunity is the state of not being affected. In other words, immunity can be said as a protection mechanism. One of the first lines of protection that everyone can see for ourselves is our skin. Yes, the skin is the largest protective organ covering almost the entire body and acts as a physical barrier to the invading microbes. Sebum and sweat secreted on to the skin surface are known to contain antibacterial and antifungal substances. Even if some microbes enter the skin, mucus (a slippery fluid) secreted by the mucous membrane (a moist lining on the surface of the internal parts that are exposed to air) traps microbes and other foreign material on its sticky surface. Thus, healthy skin by acting as a waterproof and germproof barrier provides general protection of our body naturally. While the healthy skin prevents entry of microbes into the body, a healthy stomach destroys many of the microbes that enter the body through food and drinks. The hydrochloric acid present in high concentrations in the stomach kills most ingested microbes making it another major line of non-specific defense mechanism. Aside from this, tears and saliva also act as a non-specific defense agent as they contain lysozyme, an enzyme with antibacterial properties.
Immune system
So far, we have seen how our body is protected from microbes externally. Now we can see how our immune system works to fight the enemies (pathogenic bacteria, fungi, viruses, parasites, and toxic chemicals) that entered inside the body tissues. Immune system is the body’s collective defense measures and it works against the invaders. One of the first lines of defense here is the macrophages, a type of white blood cell that is localized at different places inside the body. We can consider these macrophages as police personnel of local police stations. Just like the local police personnel, who are first to reach the fighting location, macrophages are the first to reach the infected location. The macrophages eat and destroy enemies at the infected location. When the enemies are more in number and the macrophages keep fighting for a longer time, a message sent to call for neutrophils. These cells are the most common type and account for about 40% to 75% of the total amount of white blood cells. Neutrophils after receiving the message, move to the site of infection in large numbers, releases toxins, and kill the microbes very aggressively. Neutrophils help to produce interferons, which then protects adjacent cells from viruses. They also eat the microbes, destroy the damaged cells, and removes the waste materials. Neutrophils are so aggressive that they might even affect the normal healthy cells of our body. Most macrophages and neutrophils do not bother to know the type of enemy. If the fight continues for longer duration and infection is still not controlled, then another type of white blood cell called dendritic cells are activated. Maybe we can say the dendritic cells as an intelligence department. The dendritic cells collect more information about the enemies and try to understand whether the enemy is bacteria, fungi, viruses, or parasites. In other words, we can say that they identify the type of antigen. Once identified (e.g., virus), the dendritic cells instruct the immune system to produce task forces specifically to fight against the identified antigens. T cells and B cells are the two major task forces thus produced and their job is to specifically attack the antigens. T cells directly kill the virus-infected cells and B cells produce antibodies against the identified antigens (here viruses). Antibodies produced by the B cells specifically bind to the virus-infected cells and kills them and make them easier to kill by the macrophages. In the process, the immune system makes a note of the resources and effort used to kill the virus. This memory by the immune system helps to easily fight against same as well similar antigens in the future. This is called adaptive immunity as the body gets adapted to fight infection.
Four pillars in immunity
What our immune system would do if the assault is by any pathogenic agent to which, our immune system has no experience? How can we overcome or protect ourselves from such new pathogenic substances? Improving or maintaining our non-specific defense mechanisms (viz., macrophages, and neutrophils function) and providing our body with adequate resources is a key to protect us from new infection or manage the infection effectively.
Healthy diet, exercise, sleep and happiness are the natural ways to help us maintain a healthy non-specific defense system.
Healthy diet and immunity
A Healthy diet is one of the most important resources, the body needs daily. We have seen that, during an infection, a fight is happening between the intruders (pathogens) and our white blood cells. Obviously, energy gets depleted during the fight. Longer the fight, more the energy utilized. The loss in energy can be compensated by eating healthy foods that provide adequate essential nutrients viz., carbohydrates, proteins, fats, vitamins, and minerals. Taking wholesome foods and enough of good quality water are important component of a healthy diet. Additionally, consuming antioxidants in the form of fruits is very helpful.
Exercise and immunity
Regular moderate exercise is very important for people with a sedentary lifestyle. We have seen that physically active individuals are less susceptible to viral and bacterial infections than sedentary individuals irrespective of age. Thus, the importance of regular moderate exercise cannot be overstated, even if we say it improves immunity. Studies in animals and humans also indicated the benefit of physical exercise. Microbe eating capacity (phagocytic activity) of macrophages was found to be increased in a study in rats1 and mice2 because of exercise. Muscle macrophage function may get compromised due to obesity, aging, and a sedentary lifestyle. Muscle macrophage function was reported to be improved after an endurance exercise training in humans.3 Regular Yoga practice including Pranayama was reported to reduce stress indicators, improve antioxidant status and immunity in a study in humans.4
A review article published in the North American Journal of Medical Sciences talked about various health benefits of yogic practices including Pranayama and Meditation.5 In a randomized controlled study involving first-year MBBS students, regular yogic practices of 35 minutes/day for 12 weeks helped maintain immunity and reduce stress levels during their medical term–academic examination compared to the control group where immunity in terms of IFN-γ was significantly decreased and stress in terms of cortisol (a stress hormone) was significantly increased.6 IFN-γ helps in the activation of macrophages and thus provides immunity against viral and bacterial infections.
Sleep and immunity
Good sleep is essential to maintain immunity. Insufficient sleep is known to compromise immunity.7 Shorter sleep duration prior to viral exposure was reported to increase susceptibility to the common cold.8 The physically active day brings good sleep.
Happiness and immunity
Happiness is important for our well-being. Happiness is a sustainable state of self-attainment and is a positive emotion. We can be stressed and feel sad (negative emotion) if we do not want to be in good health. But that’s not the case and we all wanted to be healthy. So, let us be happy. During visits of the Smiling Hospital Foundation’s Artists, lymphocytes of hospitalized children were found to be increased compared to the control group. During each visit, children were given more attention and care (positive emotion).9 A biologist tried to identify how the mind influences physical health and came to the conclusion that positive emotions can override the biological effects of adversity.10 A review article indicates that individuals characterized by a more negative affective style show poor immune response and may be at risk for illness more so than those with a positive affective style.11
To conclude, I would like to say that diet, exercise, sleep, and happiness are four pillars of a healthy life. An uncontrolled increase or decrease in any of these pillars is detrimental to health. Do you know that four pillars of healthy life also prevents lifestyle diseases. Check this title “Healthy lifestyle, an approach to prevent lifestyle diseases” to know more.
Note: What we know is very little and what we do not know might be equal to what is happening inside every living cell. The immune system is highly complex and the information provided here on how our immune system works is a simplified overview.
Disclaimer: This article was written and published by Muruganantham in LinkedIn. The same article with little modification is presented here for the benefit of people who visit this website.
