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  • Arijit Bhattacharya

Asthma And Its Immunological Aspect



Asthma is a chronic inflammatory disease that affects our respiratory system and causes bronchial hyper-reactivity, mucus overproduction, and airway narrowing. It leads to shortness of breathing, suffocation, and wheezing. Asthma is a prevalent medical condition. According to a survey, almost 1 in 10 children and 1 in 12 adults are affected, and worldwide 300 million people are affected by Asthma.

On immunological basis, asthma can be differentiated into:

Eosinophilic Asthma:

Eosinophilic asthma (EA) is a severe type of asthma. High eosinophils in the blood mark it; these white blood cells cause inflammation and swelling in the airways and respiratory system. The higher the levels of eosinophils in the blood, the more severe asthma symptoms can be. High levels of eosinophils can develop when the body fights off a parasitic infection, or respiratory infection can cause this type of asthma. To treat this type of asthma, antibiotics can also be included with other asthma medications.


Neutrophilic Asthma:


Neutrophilic asthma (NA) is very complex and less clearly understood. Patients with neutrophilic asthma have a high neutrophil count in the sputum ranging from 40% to 76% of sputum cells. Increased neutrophils in the sputum have been associated with severe persistent asthma, fixed airway obstruction, and it can also be caused by Pneumonia. The disease tends to be worse at night, so it is also known as nocturnal asthma. Some Anti-inflammatory agents, Nebulizers, are effective medications to treat this type of asthma.


Body’s immunological response in case of Asthma:


Pic: nature.com

Epithelial cell–DC interactions during the sensitization and challenge phase of experimental asthma. Both lung cDCs and epithelial cells express pattern-recognition receptors and can be activated directly by allergens. In response to allergens, lung epithelial cells produce chemokines that attract immature pre-cDCs. Activated epithelial cells produce ‘instructive’ cytokines (for example, IL-25, IL-33 ) and danger signals (ATP and uric acid) that favor the maturation of CD11b+ cDCs. Activated lung CD11b+ cDCs then migrate. In the lymph nodes, DCs receive help from basophils to sustain TH2 responses. When the lungs are repeatedly exposed to allergens, poorly migratory monocytic DCs and macrophages could locally restimulate effector function in lung-resident lymphocytes.


Overlap syndromes and Respiratory viral infection:

Overlap syndromes:

Eosinophilic asthma is an exclusive TH2 disorder, and neutrophilic asthma is an exclusive TH17 disorder. In many cases, there is considerable overlap in the types of cytokines found in an asthma endotype related to the severity of the disease. In this case, IL-18 drives the activation of TH1 cells that produce IL-13 and cause severe BHR ( Bronchial Hyper Reactivity ), which raises the serum levels of this cytokine and causes acute asthma attacks.

Respiratory viral infection:

Pic: Lungs Disease News

This is caused by relatively mild respiratory viruses, such as human rhinovirus (HRV), adenovirus, or influenza. Respiratory viruses can induce an innate immune response that leads to the activation of natural killer T cells and macrophages. Some asthmatics with low innate antiviral immunity can be more susceptible to viral infections. Also, the infection with HRV-16 in asthmatics causes neutrophilic inflammation and steroid resistance.


Detection of Asthma:

Symptomatic investigation and Physical examination are the main procedure for the detection of Asthma. Apart from these investigations, the primary and most common test to detect Asthma is PFT or Pulmonary Function Test. Some other diagnostic tests are also required to see the leading cause and severity of Asthma, and these tests include

  1. Lungs X-Ray

  2. CT-Scan

  3. Allergy tests

Treatment Options:

  • Inhalers: An inhaler is a medical device used to deliver medication directly into the lungs. This is the most common and effective way to treat asthma. Some common inhaler drugs are Corticosteroids, Fluticasone, Salbutamol, etc.

  • Nebulizers: Nebulizer is a type of medical device that changes medication from liquid to mist form to directly go into lungs cells. Nebulizers provide more effective and quick treatment in the case of asthma and COPD. Albuterol, epinephrine are some commonly used medications that are used to deliver through a nebulizer.

  • Anti-Allergic & Steroid Drugs: These drugs are used to prevent the body’s allergic reaction and reduce the inflammation of lungs cells. Ex; Montelukast, Zileuton, Prednisone etc...


  • Bronchial thermoplasty: It is a bronchoscopic procedure for the treatment of severe and uncontrolled asthma. It prevents the tightening of airway cells by using a heated electrode.

Conclusion:

Asthma is a common and chronic respiratory disorder that can affect anyone of any age. Most symptoms are mild but severe types of asthma should be treated on time, or it can be life-threatening.

Specific therapy and medications can control asthma and prevent irreversible airway changes in asthmatic patients. To avoid any complications, asthmatic patients should avoid allergens and should carry inhalers for emergency purposes. In future monoclonal antibodies, research can be an effective treatment for asthmatic patients to develop their immunity.


Reference:

  1. Kuby Immunology| Eighth Edition| Jenni Punt; Sharon Stranford; Patricia Jones; Judy Owen

  2. https://www.lung.org/lung-health-diseases/lung-disease-lookup/asthma

  3. The Immunology of Asthma and Allergic Rhinitis. Kiboneka, Andrew, and Dan Kibuule.

  4. Lambrecht, Bart N, and Hamida Hammad. “The Immunology of Asthma.” Nature Immunology, vol. 16, no. 1, 18 Dec. 2014, pp. 45–56, www.nature.com/articles/ni.3049, 10.1038/ni.3049

  5. World Health Organization. “Asthma.” WHO, 3 May 2021.


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