Is Your Immune System Making Your Asthma Worse?

The immune system plays a central role in the onset and severity of asthma. At its heart, asthma is a disease characterized by an overactive immune response in which the body reacts aggressively to environmental triggers by releasing cells that incite inflammation in the airways. The abrupt rise in inflammation causes the airways to narrow and spasm, leading to the shortness of breath, wheezing, cough, and chest tightness that people recognize as asthma.

Asthma was once thought to solely be caused by changes in one's acquired (adaptive) immune response. However, there is increasing evidence that the way in which we live as a society has given rise to diseases like asthma by altering the inborn (innate) immune response.

Woman with a cold blowing her nose
Michael H/Getty Images 

The Impact of Inflammation

The immune system coordinates your body's defenses to infection and disease. When confronted by anything that can cause the body harm, the immune system will release a variety of white blood cells that target and neutralize the disease-causing invaders (pathogens).

These include monocytes that instigate the generalized frontline assault (a.k.a. innate immunity) and B cells and T cells that are tailor-made to recognize and target the specific pathogen (a.k.a. adaptive immunity).

As part of the immune assault, white blood cells release a variety of substances, called cytokines, into the bloodstream. These cytokines provoke an inflammatory response, causing tissues and blood vessels to swell abnormally so that larger immune cells are able to access to the site of the infection or injury.

Inflammation is a beneficial response that speeds the resolution of illness and starts the healing process. But it is also one that can cause localized pain, swelling, sensitivity, and redness in the affected tissues.

Triggers and Asthma

As essential as inflammation is when it comes to the body's defenses, it can cause harm if it is provoked inappropriately. Such is the case with diseases like asthma in which the body overacts to environmental triggers that are generally of little to no harm to the human body.

In people with asthma, the immune system will respond to these triggers by activating inflammation in the airways of the lungs, called the bronchi and bronchioles. This will cause them to narrow (bronchoconstriction), contract involuntarily (bronchospasm), and secrete excess mucus, leading to symptoms of asthma.

Against the backdrop of chronic inflammation, the airways will become increasingly hyperresponsive, meaning that the tissues will become extra-sensitive to triggers and more likely to provoke an asthma attack.

Infections' Impact on Asthma

Asthma can be triggered by a variety of things. One of the most common triggers are infections, including respiratory viruses and, to a lesser degree, bacterial and fungal infections of the respiratory tract.

Respiratory viruses are the predominant infectious cause of asthma attacks. As the viruses attach to receptors on the lining of the airways, they effectively "trip the alarms" for the immune system to attack, leading to inflammation and the onset of acute asthma symptoms.

In some cases, the symptoms of the infection will precede the attack; in others, the infection and asthma symptoms will co-occur.

Among the respiratory viruses closely link to asthma symptoms are:

Viral-induced asthma is extremely common, affecting roughly 85% of children and 50% of adults with asthma.

Less commonly, bacteria like Streptococcus pneumoniae, Hemophilus influenzae, and Moraxella catarrhalis have been known to trigger asthma attacks, particularly if a sinus infection is involved.

Fungal infections are more closely associated with poor asthma control rather than that onset of an attack, although it can occur.

Asthma-Related Risk of Infection

On the flipside, asthma can increase the risk of respiratory infections, in part because persistent inflammation can compromise the integrity of the lining of the airways. This can provide infectious pathogens easier access into deeper tissues of the lungs, leading to severe lower respiratory infections such as pneumococcal pneumonia and Bordetella pertussis (whooping cough).

Poor control of asthma is a major risk factor for the development of secondary infections as it allows inflammatory damage to persist unimpeded. Certain medications, like corticosteroids, can also compromise airway tissues and increase the risk of infection.

There is also evidence that the adaptive immune response in people with asthma can become less robust over time and begin to "forget" pathogens it has previously been exposed to. The reasons for this are not entirely clear, but it is evidenced in part by increased rates of non-respiratory infections in people with asthma, including skin infections, genital infections, urinary tract infections, and gastrointestinal infections.

People with asthma are also more likely to experience the reactivation of previous infections. One example is shingles, a disease caused by the reactivation of the chickenpox virus, which strikes people with asthma twice as often as those without.

When Allergies Strike

Allergens (generally harmless substances that trigger allergy symptoms) can also trip the immune system and trigger attacks in some, but not all, people with asthma. Those affected will have a form of the disease called allergic (or atopic) asthma.

There are both atopic and non-atopic forms of asthma. By definition, atopic diseases are those characterized by an exaggerated immune response to allergens. Atopic asthma affects as many as 80% to 90% of people with asthma to some degree and is by far the most common form of asthma.

The onset of asthma symptoms in people with allergies mostly starts in the epithelial cells that line the airways. When airborne allergens are introduced into the lungs, such as pollen or pet dander, the immune system activates immune cells in the epithelium and sets off a series of events referred to as the allergic cascade.

This not only causes allergy symptoms (including sneezing, watery eyes, runny nose, and itching) but stimulates the production of a type of white blood cell known as an eosinophil. The accumulation of eosinophils in the airways triggers the rapid rise of inflammation and, in turn, the development of acute asthma symptoms.

Food allergies are also associated with asthma but don't so much trigger asthma symptoms as increase the likelihood of a severe attack.

The Allergic Cascade

The allergic cascade generally occurs in the following steps. Though involved, this process happens quickly, though it's possible that related breathing troubles could linger for a day:

  1. Allergen exposure: The body is exposed to an allergen. Epithelial cells lining the airways, skin, and digestive tract are among the primary sites where the allergic response is triggered.
  2. IgE production: The immune system responds by instructing B cells to secrete immunoglobulin E (IgE) into the bloodstream This is a type of antibody that recognizes only that allergen.
  3. IgE attachment: The IgE antibody attaches to receptors on mast cells (a type of granulocyte implanted in tissues throughout the body) and basophils (a type of white blood cell circulating freely in the blood).
  4. Degranulation: The attachment causes mast cells and basophils to degranulate (break open). The degranulation causes the release of inflammatory compounds, including histamine and chemotactic factors, in and around the affected tissues.
  5. Immediate reaction: The release of histamine and other inflammatory substances causes the body to have an immediate allergic reaction within minutes. The response, which may include rash, itching, and sneezing, usually reaches its peak in 15 minutes and goes away after 90 minutes.
  6. Late-phase reaction: The release can also trigger a late-phase reaction within hours by attracting eosinophils and other white blood cells to the site of the allergic reaction. In the late-phase reaction, respiratory symptoms like nasal swelling, shortness of breath, and cough can persist for up to 24 hours.

The accumulation of eosinophils not only provokes inflammation, triggering an attack, but floods the airways with chemicals that can irritate and damage tissues, increasing hyperresponsiveness.

Non-Allergic Asthma

Non-allergic asthma, also known as non-atopic asthma or intrinsic asthma, is another form of the disease triggered by factors other than allergies. The inflammatory processes are similar to that of allergic asthma (including mast cell activation and eosinophilia) but do not involve IgE.

Non-allergic asthma is a less common form of asthma, accounting for 10% to 30% of all cases, and is more common in adults than children.

Non-allergic asthma can be triggered by a variety of things, including:

Given the diversity of triggers, it is not entirely clear what causes non-allergic asthma. Some scientists believe that autoantibodies involved in autoimmune diseases play a central role. This is evidenced in part by increased rates of certain autoimmune diseases like type 1 diabetes, myasthenia gravis, and lupus in people with asthma.

There other similarities that suggest a relationship between asthma and autoimmunity. For example, mast cell activation is believed to be involved in the onset of acute symptoms of autoimmune diseases like rheumatoid arthritis and multiple sclerosis.

Stress and extreme temperatures are also known to influence many autoimmune diseases, including lupus, gout, and psoriasis.

Atopy and the Risk of Asthma

The immune system is not only involved in the frequency and severity of asthma symptoms but also plays a major role in the onset of the disease. As much as a person's genetics contributes to the risk of asthma, the way that the immune system responds to the environment plays a major role.

Asthma is believed to be a part of the progression of diseases referred to as the atopic march. The hypothesis, gaining acceptance among scientists, contends that atopy occurs in stages as one atopic disease gives rise to another.

The atopic march tends to progress in a consistent pattern, involving:

  1. Atopic dermatitis (eczema)
  2. Food allergies
  3. Asthma
  4. Allergic rhinitis (hay fever)

The atopic march is believed to start during infancy with the onset of eczema, a disease that most often affects babies between the ages 3 and 6 months.

In children with eczema, otherwise harmless substances can enter the body through breaks in the skin and trigger a response from an immune system not yet able to recognize the substance as harmless. In doing so, it leaves behind "memory" cells that will trigger an inappropriate immune response whenever the harmless substance reappears.

These foundational changes to the immune system can give rise to food allergies by making it hyperresponsive to food proteins that it is either not familiar with or deprived of. This, in turn, can instigate additional changes that give rise to asthma and hay fever.

The progression of the atopic march can vary but most typically starts with eczema, a disease that affects between 80% and 90% of children by the age of 5.

Asthma and the Hygiene Theory

Other factors that can predispose a person to atopic diseases is the lack of contact with substances that build a healthy immune response. It a hypothesis referred to as the "hygiene theory."

The hygiene theory posits that an industrialized lifestyle—characterized by better sanitation, greater infection control, and frequent antibiotic use—deprives a child of exposure to microbes needed to build a robust immune response.

One such example is the avoidance of peanuts in young children, an action that can increase the risk of a peanut allergy. By contrast, exposing a baby to peanuts before 6 months decreases the risk.

In a similar vein, studies have shown that living on a farm from birth decreases the risk of asthma. This suggests that contact with animals, including pets, can be protective against asthma by exposing the immune system to pet dander, bacteria, and other microbes at an early age.

What You Can Do

This is clearly complex, and there is only so much you can do to alter your response to the immunologic triggers of asthma.

One of the primary tools used to control an overactive immune response are asthma medications. Some non-drug strategies can be helpful complements as well.

Medications

Drugs that help temper airway inflammation can do so locally or systemically, or block specific stages of the allergic cascade.

Among the commonly prescribed asthma medications are:

Key to the control of asthma symptoms is the consistent use of asthma medications. This is especially true with inhaled corticosteroids and LABAs, whose therapeutic effects decline rapidly if not use daily as prescribed.

People who take their daily asthma medications as prescribed are 67% less likely to have a severe attack, 62% less likely to be hospitalized, and 52% less likely to have functional limitations than people with suboptimal adherence.

Lifestyle and Self-Care Strategies

Beyond medications, there are things you can do to prevent immune overreaction if you have asthma:

  • Identify and avoid asthma triggers. Avoiding asthma triggers is arguably more beneficial than treating asthma symptoms. These may include allergens, irritants, stress, and certain medications.
  • Treat respiratory infections aggressively. Doing so decreases the risk of viral-induced asthma. This includes colds, sinusitis, flu, and other upper or lower respiratory infections.
  • Get the annual flu vaccine. Influenza immunization is one of the most important things to do if you have asthma. Many people get their shots in October, but it may be best to get yours earlier if you are prone to severe attacks.
  • Avoid crowds during cold and flu season. This includes public gatherings and enclosed spaces like airplanes. If you need to travel by air, wear a face mask.
  • Take antihistamine prophylaxis. If you are prone to severe asthma during hay fever season, a daily antihistamine (referred to as antihistamine prophylaxis) can mitigate the effects of histamines and reduce the risk of an asthma attack.
  • Check the pollen count. People who react severely to pollen should keep track of the pollen count and stay indoors if it is high. Close all doors and windows, and use an air conditioner to keep the temperature cool.
  • Warm up and cool down during exercise. If exercise is an asthma trigger, avoid endurance sports or exercising aggressively. Gradually warming up and cooling down, along with taking regular exercise breaks, can help regulate body temperature and prevent an overactive immune response.
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