WHO Definition of Immunity

The term immunity is medically defined as a condition of being immune. Immunity confers the ability to resist disease, through the activities of the immune system.The development of immunity to a pathogen through natural infection is a multi-step process that typically takes place over 1-2 weeks according to the World Health Organization (WHO). Immunization is the process by which a person is made immune or resistant to an infectious disease, typically by the administration of a vaccine. Vaccines stimulate the body’s own immune system to protect the person against subsequent infection or disease. There are 3 types of immunity namely:

Active immunity: occurs when our own immune system is responsible for protecting us from a pathogen. Individuals rely on active immunity more so than passive immunity. Active immunity is created by our own immune system when we are exposed to a potential disease-causing agent (i.e., pathogen). Most of the time, we are exposed to these potential pathogens naturally throughout the course of our day — in the air we breathe, the food we eat, and the things we touch. Luckily, most of these exposures are to agents that will not result in disease, either because they are harmless or because our immune system works to neutralize them.

In addition to “fighting off” these pathogens, active immunity is important because it lasts a long time in the form of immunologic memory. Immunologic memory consists of B and T cells that can recognize a particular pathogen. These cells circulate at low levels in our bodies and if “activated” by recognizing that pathogen in their travels, they quickly start to multiply and signal other elements of the immune system to activate as well.

Passive immunity: occurs when we are protected from a pathogen by immunity gained from someone else. Passive immunity, or immunity gained in a way other than from one’s own immune system, can occur in a few ways and can be life-saving. However, passive immunity is short-lived because the antibodies are not continually replenished as they would be in an individual whose immune system is responding directly. Passive immunity can occur in a couple of ways:

 

Maternal antibodies

Unborn and newly born babies are protected by antibodies from the maternal immune system. These antibodies are shared in two ways: across the placenta and in breast milk.

 

Placenta and circulation — When a woman is pregnant, her blood circulates through the placenta to deliver nourishment and protection to the developing fetus. As the blood circulates, so do the antibodies and immune system cells that travel in blood. Although developing fetuses are not typically exposed to any pathogens in utero, they are exposed to viruses and bacteria during and immediately after birth. The types and levels of antibodies in a baby’s blood at birth reflect those of the mother.

Breast milk — Babies also get antibodies from breast milk, particularly from a protein-rich version of breast milk supplied in the first few days after birth known as colostrum. Colostrum, which is produced in the first three to five days after birth, contains higher levels of antibodies that protect the intestinal surface (immunoglobulin A or IgA) and lower levels of nutritional ingredients than milk produced in the weeks following birth. This transfer of antibodies from mother to child suggests its importance in the period before a baby’s immune system can generate its own protection.

 

Immunoglobulin treatments

In certain situations, antibodies obtained from animals, from other people, or synthesized in a laboratory can be used to treat individuals at risk of infections. For example, infants born to women infected with hepatitis B are treated with antibody preparations in addition to being vaccinated in an effort to protect them from also becoming infected with hepatitis B. In another example, people bitten by some poisonous snakes may be treated with antivenom, a mixture of antibodies against the type of snake venom to which the person was exposed.

 

Community immunity

Community immunity occurs when people are protected by those around them. This type of protection is indirect in that it does not involve physical components of immunity, such as antibodies, but rather results when a pathogen is less likely to infect a susceptible person because of the high numbers of protected people around them. Because this immunity is not based on “products” of the immune system, it is the least reliable. However, for some in our communities, such as those too young to be immunized or those with weakened immunity due to illness or treatment, community immunity is the only way they can be protected.

 

How can you improve your immune system?

On the whole, your immune system does a remarkable job of defending you against disease-causing microorganisms. But sometimes it fails: A germ invades successfully and makes you sick. Is it possible to intervene in this process and boost your immune system? What if you improve your diet? Take certain vitamins or herbal preparations? Make other lifestyle changes in the hope of producing a near-perfect immune response?

 

What can you do to boost your immune system?

The idea of boosting your immunity is enticing, but the ability to do so has proved elusive for several reasons. The immune system is precisely that — a system, not a single entity. To function well, it requires balance and harmony. There is still much that researchers don’t know about the intricacies and interconnectedness of the immune response. For now, there are no scientifically proven direct links between lifestyle and enhanced immune function.

But that doesn’t mean the effects of lifestyle on the immune system aren’t intriguing and shouldn’t be studied. Researchers are exploring the effects of diet, exercise, age, psychological stress, and other factors on the immune response, both in animals and in humans. In the meantime, general healthy-living strategies are a good way to start giving your immune system the upper hand.

  • Maintain a healthy weight.
  • If you drink alcohol, drink only in moderation.
  • Get adequate sleep.
  • Take steps to avoid infection, such as washing your hands frequently and cooking meats thoroughly.
  • Try to minimize stress.

 

Increase immunity the healthy way

Many products on store shelves claim to boost or support immunity. But the concept of boosting immunity actually makes little sense scientifically. In fact, boosting the number of cells in your body — immune cells or others — is not necessarily a good thing. For example, athletes who engage in “blood doping” — pumping blood into their systems to boost their number of blood cells and enhance their performance — run the risk of strokes.

Attempting to boost the cells of your immune system is especially complicated because there are so many different kinds of cells in the immune system that respond to so many different microbes in so many ways. Which cells should you boost, and to what number? So far, scientists do not know the answer. What is known is that the body is continually generating immune cells. Certainly, it produces many more lymphocytes than it can possibly use. The extra cells remove themselves through a natural process of cell death called apoptosis — some before they see any action, some after the battle is won. No one knows how many cells or what the best mix of cells the immune system needs to function at its optimum level.

Immune system and age

As we age, our immune response capability becomes reduced, which in turn contributes to more infections and more cancer. As life expectancy in developed countries has increased, so too has the incidence of age-related conditions.

While some people age healthily, the conclusion of many studies is that, compared with younger people, the elderly are more likely to contract infectious diseases and, even more importantly, more likely to die from them. Respiratory infections, influenza, the COVID-19 virus and particularly pneumonia are a leading cause of death in people over 65 worldwide. No one knows for sure why this happens, but some scientists observe that this increased risk correlates with a decrease in T cells, possibly from the thymus atrophying with age and producing fewer T cells to fight off infection. Whether this decrease in thymus function explains the drop in T cells or whether other changes play a role is not fully understood. Others are interested in whether the bone marrow becomes less efficient at producing the stem cells that give rise to the cells of the immune system.

A reduction in immune response to infections has been demonstrated by older people’s response to vaccines. For example, studies of influenza vaccines have shown that for people over age 65, the vaccine is less effective compared to healthy children (over age 2). But despite the reduction in efficacy, vaccinations for influenza and S. pneumoniae have significantly lowered the rates of sickness and death in older people when compared with no vaccination.

 

There appears to be a connection between nutrition and immunity in the elderly. A form of malnutrition that is surprisingly common even in affluent countries is known as “micronutrient malnutrition.” Micronutrient malnutrition, in which a person is deficient in some essential vitamins and trace minerals that are obtained from or supplemented by diet, can happen in the elderly. Older people tend to eat less and often have less variety in their diets. One important question is whether dietary supplements may help older people maintain a healthier immune system. Older people should discuss this question with their doctor.

Diet and your immune system

Like any fighting force, the immune system army marches on its stomach. Healthy immune system warriors need good, regular nourishment. Scientists have long recognized that people who live in poverty and are malnourished are more vulnerable to infectious diseases. Whether the increased rate of disease is caused by malnutrition’s effect on the immune system, however, is not certain. There are still relatively few studies of the effects of nutrition on the immune system of humans.

There is some evidence that various micronutrient deficiencies — for example, deficiencies of zinc, selenium, iron, copper, folic acid, and vitamins A, B6, C, and E — alter immune responses in animals, as measured in the test tube. However, the impact of these immune system changes on the health of animals is less clear, and the effect of similar deficiencies on the human immune response has yet to be assessed.

So, what can you do? If you suspect your diet is not providing you with all your micronutrient needs — maybe, for instance, you don’t like vegetables — taking a daily multivitamin and mineral supplement may bring other health benefits, beyond any possibly beneficial effects on the immune system. Taking megadoses of a single vitamin does not. More is not necessarily better.

Improve immunity with herbs and supplements?

Walk into a store, and you will find bottles of pills and herbal preparations that claim to “support immunity” or otherwise boost the health of your immune system. Although some preparations have been found to alter some components of immune function, thus far there is no evidence that they actually bolster immunity to the point where you are better protected against infection and disease. Demonstrating whether an herb — or any substance, for that matter — can enhance immunity is, as yet, a highly complicated matter. Scientists don’t know, for example, whether an herb that seems to raise the levels of antibodies in the blood is actually doing anything beneficial for overall immunity.

Stress and immune function

Modern medicine has come to appreciate the closely linked relationship of mind and body. A wide variety of maladies, including stomach upset, hives, and even heart disease, are linked to the effects of emotional stress. Despite the challenges, scientists are actively studying the relationship between stress and immune function.

For one thing, stress is difficult to define. What may appear to be a stressful situation for one person is not for another. When people are exposed to situations they regard as stressful, it is difficult for them to measure how much stress they feel, and difficult for the scientist to know if a person’s subjective impression of the amount of stress is accurate. The scientist can only measure things that may reflect stress, such as the number of times the heart beats each minute, but such measures also may reflect other factors.

Most scientists studying the relationship of stress and immune function, however, do not study a sudden, short-lived stressor; rather, they try to study more constant and frequent stressors known as chronic stress, such as that caused by relationships with family, friends, and co-workers, or sustained challenges to perform well at one’s work. Some scientists are investigating whether ongoing stress takes a toll on the immune system.

But it is hard to perform what scientists call “controlled experiments” in human beings. In a controlled experiment, the scientist can change one and only one factor, such as the amount of a particular chemical, and then measure the effect of that change on some other measurable phenomenon, such as the amount of antibodies produced by a particular type of immune system cell when it is exposed to the chemical. In a living animal, and especially in a human being, that kind of control is just not possible, since there are so many other things happening to the animal or person at the time that measurements are being taken.

Despite these inevitable difficulties in measuring the relationship of stress to immunity, scientists are making progress.

Does being cold give you a weak immune system?

Almost every mother has said it: “Wear a jacket or you’ll catch a cold!” Is she right? Probably not, exposure to moderate cold temperatures doesn’t increase your susceptibility to infection. There are two reasons why winter is “cold and flu season.” In the winter, people spend more time indoors, in closer contact with other people who can pass on their germs. Also the influenza virus stays airborne longer when air is cold and less humid.

But researchers remain interested in this question in different populations. Some experiments with mice suggest that cold exposure might reduce the ability to cope with infection. But what about humans? Scientists have dunked people in cold water and made others sit nude in subfreezing temperatures. They’ve studied people who lived in Antarctica and those on expeditions in the Canadian Rockies. The results have been mixed. For example, researchers documented an increase in upper respiratory infections in competitive cross-country skiers who exercise vigorously in the cold, but whether these infections are due to the cold or other factors  such as the intense exercise or the dryness of the air is not known.

A group of Canadian researchers that has reviewed hundreds of medical studies on the subject and conducted some of its own research concludes that there’s no need to worry about moderate cold exposure it has no detrimental effect on the human immune system. Should you bundle up when it’s cold outside? The answer is “yes” if you’re uncomfortable, or if you’re going to be outdoors for an extended period where such problems as frostbite and hypothermia are a risk. But don’t worry about immunity.

Exercise: Good or bad for immunity?

Regular exercise is one of the pillars of healthy living. It improves cardiovascular health, lowers blood pressure, helps control body weight, and protects against a variety of diseases. But does it help to boost your immune system naturally and keep it healthy? Just like a healthy diet, exercise can contribute to general good health and therefore to a healthy immune system. It may contribute even more directly by promoting good circulation, which allows the cells and substances of the immune system to move through the body freely and do their job efficiently. SEE: National Program on Immunization (NPI) Schedule In Nigeria

 

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