Immunity And Chronic Diseases

Chronic diseases may or may not respond to medication and vaccination. Hence, prevention is always better than cure when it comes to these ailments, which include autoimmune diseases like rheumatoid arthritis, cancer, cardiovascular diseases, diabetes, and Alzheimer's disease, among others.

The World Health Organization (WHO) defines chronic diseases as Non-Communicable Diseases (NCDs). Smoking, alcohol abuse, unhealthy dietary habits, along with genetic and environmental factors are primarily held responsible for triggering NCDs. Thus, avoiding excessive smoking, drinking alcohol, eating unhealthy (junk, processed, fried) food; and keeping one's weight in control with healthy food and optimum exercise are considered vital for preserving one's immunity to prevent chronic diseases.

How does low immunity lead to chronic diseases?

The human immune system comprises a complex network of cells, tissues, and organs, that work in sync with each other to fight the infection-causing micro-organisms that attack the body.

The immune system recognises potentially harmful substances as antigens (which can also include toxins or certain chemicals). It sets off an immune response, whose job is to make antibodies to kill the antigens, and attack them.

The immune system also memorises the antigen and sends out the effective antibodies whenever it attacks the body again.

This whole process is called immunity, and when in sync, is what keeps us healthy and alive.

However, when the immune system starts faltering in preparing or sending the antibodies, or worser still, if it misreads the signals and starts attacking the body's own healthy organs, that is when a person becomes immunocompromised or gets autoimmune.

Both these states can lead to chronic diseases.

Problems of the immune system

Certain external and internal factors can disbalance the human immune system. Let us take a look at them:

1. Genetic immunodeficiencies

At times, a person's immune system is compromised by birth, due to certain mutations or variations in their genes. For instance, T cells do not develop or mature enough to provide the requisite amount of immunity, thus causing severe combined immune deficiency aka SCID. Chronically low levels of neutrophils (the first type of WBCs to respond to invading antigens) can cause Kostmann syndrome that increases the chances of getting bone marrow cancer.

2. Certain medication

Cancer cures can sometimes lead to a weakened immune system. Depending on which drugs are being used and the periodicity of the therapy, chemotherapy can cause a decrease in neutrophils aka neutropenia.

Also, depending on the size of the dose and the amount of body exposed to it, radiation therapy can lead to low WBCs, thus suppressing the person's immunity. Apart from that, biologics that're usually prescribed to tone down an autoimmune condition, can lead to immunosuppression. So also, corticosteroids that're prescribed for allergies, asthma, and organ transplant among others.

3. Infections

While infections like measles, mononucleosis, and flu can weaken the immune system for a short duration, heavier infections like HIV can lead to chronic immune system disorders.

4. Stress, diet, sleep

Excessive stress releases cortisol which has a negative effect on the immune system if released continuously for extended periods. A diet low in nutrients and high in added sugars or salt etc., can trigger proinflammatory cytokines, slow down the response of immune cells like phagocytes and neutrophils, and can disbalance the gut microbiome to produce more bad bacteria than good. Lack of quality sleep decreases the production of infection- and inflammation-fighting cytokines.

5. Overzealous immune system

On the other end of the spectrum, is autoimmunity, wherein the variations in genes, or, external factors like the environment or lifestyle habits can cause the B and T cells to rearrange genes in a faulty way. When this happens, the immune system starts attacking the body's own organs, thus leading to development of chronic autoimmune diseases.

All these factors are contributory to raising the risk of chronic diseases as a whole.

Various chronic diseases caused by immunity problems

Chronic diseases and immunity share a cyclical relationship wherein low immunity leads to chronic diseases, and the setting in of chronic diseases leads to further weakening of the immune system.

Hence, it is pertinent to preserve one's good immunity to protect oneself from chronic diseases, so as to protect from further immunocompromise.

Let's take a look at the major chronic ailments that can set in when immunity is low.

1. Heart disease

Cardiovascular diseases (CVDs), commonly known as heart diseases, are those that can affect the heart and blood vessels. According to WHO statistics, CVDs are the topmost cause of global deaths.

While CVDs can be caused by unhealthy diet, stress, smoking etc., low immunity is a pertinent factor that leads to this chronic problem, especially coronary artery disease.

The coronary artery is the most important pathway for sending oxygen and nutrients to the heart. It gets blocked due to excessive lipids (loaded with cholesterol) start building up, causing plaque to form in the vessels.

The cholesterol crystals in the plaque cause molecules to be released from the immune system. These molecules look at the crystals as foreign agents to be attacked; but when excessive molecules are released, it can cause inflammation due to overstimulation of the immune system. This, in turn, causes plaque instability and blood vessel injury, with the end result being heart attacks, strokes and probably, death.

In fact, disbalance in the immune response following reparative surgery after a heart attack, can lead to production of proinflammatory cytokines and other inflammatory mediators, which can have adverse effects on the organ, as well as, its healthy recovery.

On the flip side, heart disease can also be responsible for lowering your immunity before and after treatment. Before treatment, the sheer build-up of bad cholesterol, or the contributory factors like smoking or diabetes, make the immune system deficient. After treatment, some medications like angiotensin converting enzyme (ACE) inhibitors that are given for recovery after a heart attack, can lower the system's ability to fight serious bacterial infections, thus also compromising the immune system.

2. Diabetes

While low immunity is not a cause for people getting afflicted with diabetes, once it sets in, diabetes can become extremely detrimental for a person's immune health.

In people with Type 1 diabetes, the immune system starts attacking the insulin-producing beta cells that are found only in the pancreas. Research shows that a particular type of protein-based enzyme - 12-LO- found in beta cells, create lipids that lead to inflammation of the beta cells.

This inflammation destroys the beta cells, and when the beta cells die, it becomes impossible for the body to produce enough insulin required to regulate blood-glucose levels. This leads to serious health complications; possibly, even death.

Type 2 Diabetes (T2D) is a metabolic disorder characterised by insufficient production of insulin by the pancreas and high insulin resistance. T2D can lead to a weak immune system, apart from many other problems like chronic heart disease and kidney disease.

When the pancreas stops producing enough insulin or the body stops responding to insulin to allow glucose to be absorbed by cells, the blood glucose levels start rising higher, and in turn lead to an inflammatory response. The same phenomenon occurs due to the presence of inflammatory mediators produced by macrophages (a type of infection-fighting WBC) and adipocytes in the fat tissue.

When this inflammation continues for a long time to become chronic, it damages the pancreatic beta cells and causes hyperglycaemia. Hyperglycaemia leads to dysfunction of the immune response, thus making the person unable to fight infections, thus making him/her more vulnerable to catching infectious diseases.

The high levels of glucose in the blood release destructive molecules called dicarbonyls, which interfere with beta-defensins that are infection-controlling antimicrobial peptides. They also give a conducive environment for infection-causing microorganisms to grow unchecked.

High blood glucose content also limits and disbalances that synthesis of neutrophils, which are the first leukocytes to reach an infected area and fight infection.

3. Chronic Kidney Disease (CKD)

Kidneys are a very important, yet quite overlooked organ in the scheme of immunity.

They are a major organ for filtration of blood, maintaining circulatory pressure, and maintaining the fluid balance of the body to aid its optimal functioning.

The kidneys not just clear metabolic waste, drugs and toxins from the body, but also keep washing out bacterial toxins and cytokines that keep circulating our system.

By continuously removing the cytokines from the blood, kidneys help in controlling inflammation, and by removing the bacterial toxins, it reduces the risk of possible immune cell activation by pattern recognition receptors (PRRs).

Kidneys also help maintain the peripheral tolerance to circulating antigens like hormones and food proteins.

Ironically, the importance of kidneys in maintaining immunity becomes visible only when the immunity gets severely compromised as the kidneys almost stop functioning and clearing out the bio-waste.

When the toxins and cytokines do not get cleared as they should, the innate immune cells get activated, thus producing more cytokines and reactive oxygen species, which in turn increase the risk of tissue damage and CVDs.

Further, a decrease in the number and efficacy of lymphocytes also hampers the immunity and makes the person prone to viral-associated cancers.

On the flip side, low immunity brought about by other factors like diabetes, can harm the kidneys and cause loss of renal function.

Two types of renal diseases are caused by problems in the immune system. When the immune system begins attacking specific antigens inside the kidney, it leads to direct immune-mediated renal disease. When the immune system starts getting disbalanced due to the many factors that can affect it adversely, the kidneys can sometimes become collateral damage by getting afflicted with indirect immune-mediated renal disease.

4. Cancer

Cancer is essentially a result of unchecked cellular growth attributed to genetic malfunctioning, which leads to formation of tumours. Apart from several other factors like poor diet, stress, smoking, and radiation exposure, low immunity is a pertinent factor that can lead to cancer-causing genetic mutations.

Immunity itself can get lowered by either genetic reasons or external factors, especially age. As we grow in age, our innate immunity starts decreasing, thus allowing more genetic mutations to take place than they would earlier.

A less-than-optimally-functioning immune system has a less-than-optimally-functioning thymus gland, which does not produce enough T-cells. T cells are the first scanners of cancer cells when they start developing in the body.

Less amount of T cells fails to effectively scan the rapidly multiplying cancer cells, thus allowing a lot of them to go unchecked and thus, proliferate.

Some research shows that the process of thymus becoming less effective with progressing age, is faster in men than in women; thus, making men more prone to cancer with growing age, than women.

The fact that cancer cells can be very aggressive, also contributes to why a lowering immune system might be incapable of fighting it. Cancer cells have been seen to use deceptive signalling to prevent the growth of immature immune cells called myeloid-derived suppressive cells (MDSCs), thus helping the tumour to metastasize.

Just as low immunity leads to cancer, cancer also causes the immune system to weaken further. This happens either via the medication given for treating the cancer, or, the chronic inflammation that cancer brings along.

Except for immunotherapy (which is prescribed to boost the immune system to fight cancer cells), treatments like chemotherapy, radiation therapy, and the drugs and steroidal medication given to treat cancer can all lead to weakening the immune system as they reduce the number of white blood cells (WBCs).

Cancer also brings along chronic inflammation, which especially develops as the cancer progresses. The chronic inflammation leads to development of microbial infections (for e.g., HPV leading to cervical cancer if left untreated), immune system disbalance, and autoimmune disorders.

5. Mental health issues

There's a give n' take relation between mental health issues (which also turn chronic over a period of time) and the strength of the immune system, or the lack of it.

It has been proven that the brain and the immune system are in communication with each other, which is why a compromise of immunity can have direct effects on evolvement and progression of psychiatric disorders.

Other chronic conditions like diabetes, CVDs and autoimmune diseases which share a close connection to the disbalance of immune system, are also accompanied by psychiatric disorders, especially schizophrenia and chronic depression.

Inflammatory activation of the immune system affecting the central and peripheral nervous system is seen to increase the risk of depression. It also leads to chronic fatigue, which in turn elevates depressive tendencies in the affected person.

A disbalance in anti-inflammatory and pro-inflammatory cytokines can lead to inflammatory response which can trigger fatigue and depression.

Excessive stress produces the hormone cortisol, which disbalances the HPA axis to lead to depression and schizophrenia.

An altered neuroimmune function can also lead to autism spectrum disorders, especially in children. Chronic brain inflammation characterised especially by activated microglia (the resident immune cells of the CNS), increased inflammatory cytokines, auto-antibodies targeting the brain and CNS being produced, and an altered blood brain barrier all form the base of autism spectrum disorders.

Dysregulation of microglia is also held responsible for setting in Alzheimer's disease among older people. Microglia actually helps to clear debris from the brain, but when the production of the amyloid protein that develops in Alzheimer's patients, goes overboard, it hampers the working of the microglia, and thus contributes to progression of Alzheimer's.

In fact, age-related changes in the efficacy and functioning of B and T cells is held responsible for various kinds of dementia.

Chronic mental health issues also hamper the person's immunity.

Corticosteroid produced in stress can lower the lymphocyte count and thus hamper immunity.

Patients of depression show a higher level of central corticotropin-releasing hormone (CRH) in the CNS, which hampers the innate and peripheral immune responses.

6. Autoimmune disorders and immunity

On the other end of the spectrum, we have autoimmune disorders or autoimmune diseases, that are triggered by an overzealous immune system that cause inflammation.

In a way, most chronic diseases result from inflammation related to immune system disbalance.

Inflammation is actually a good thing, because it is the body's first line of defence against antigens such as infections, injuries or toxins.

However, excessive inflammation aka chronic inflammation is bad, because then it negatively affects various organs of the body, as seen above.

A very pertinent fallout of immunity system disorders is when the system goes into an overdrive and starts producing antibodies which attack the host body!

There are several triggers that are considered responsible for this sudden change of direction viz. obesity, infections, smoking, and heredity.

The commonest autoimmune disorders include rheumatoid arthritis, lupus, psoriasis, irritable bowel disorder, ankylosing spondylitis, type 1 diabetes, and myasthenia gravis.

People with autoimmune disorders also end up having a weak immune system because even the normal, healthy tissues are destroyed in the process of arbitrary attacks led by the awry immune system.

Conclusion

Immunity and chronic diseases are a complex relationship. Both are in an interlocked relation wherein immune system dysregulation leads to chronic diseases, and chronic diseases lead to weakening of the immune system.

The triggers for sparking this dysregulation remain common viz. stress, smoking, alcohol abuse, sleep disorders, poor diet etc.

Obesity is an interesting factor in this equation because while it is one of the predominant triggers for immune system problems, it is been declared as a chronic disease itself, since it stems from several genetic and environmental factors and takes long to shake off.

While genetics play an important role in deciding which chronic disease will creep up on an individual, it is important to control the triggers that may stroke or hasten the process.

Read for more ways to strengthen your immune system and you'll stay healthy for a longer period of time.