Atopy – Hypersensitivity, the Immune System,
Atopy is the body’s allergic process as a response to airborne allergens and usually results in inflammation and hyperactivity in the airways and various degrees of discomfort by the individual. This process does not generally refer to common sneezing or colds, but instead to hypersensitivity to distinct allergens in the environment.
The general process of atopy involves:
- The helper T cells, especially the subgroup Th2 cells. These are categories of white blood cells, or the cells in the body primarily responsible for fighting off foreign cells and infection.
- In asthmatic and allergy sufferers, these Th2 cells produce larger amounts of interleukins (Ils) than in normal individuals. Ils play a major roll in the inflammatory process.
- The interleukins 4, 9, and 13 stimulate the production and release of antibodies known as immunoglobulin E (IgE). Individuals suffering from both asthma and allergies are genetically predisposed to overproducing IgEs which bind to mast cells, specific cells of the immune system that are concentrated tin the mucus membranes, branches of the lungs, and the skin.
- When IgEs bind to mast cells, the body releases leukotrienes, chemicals designed to activate responses in the airway and mucus membranes. In general, these chemicals cause the airway to spasm, cause the body to produce excess mucus, and activate nerve endings in the airway. This is known as a first-phase asthmatic attack.
- Interleukin 5, a different chemical than those responsible for first-phase asthma attacks, attacks white blood cells called eosinophils to airways where they remain for weeks after the original attack and facilitate the release of other particles that can damage the airways.
The Immune Response in Relation to Asthma
Over the years researchers have focused on the roll of white blood cells in asthmatic responses and, until recently, targeted their research on type 2 helper cells (Th2), a type of white blood cell in the T cell category. However, in 2006, the New England Journal of Medicine published a study that found that a different type of T cell, a natural killer T cell, played a stronger roll in asthmatics than previously thought.
The study found that individuals suffering from asthma had larger numbers of these natural killer T cells in their lungs than healthy people. Although these kinds of cells are relatively rare, the researchers found that 60% of the people with moderate to severe asthma who were tested in the study had these types of cells in their lungs. The researchers discovered that this link may have an effect on the current use of corticosteroid drugs that are commonly used in asthma patients. These types of steroids target Th2 cells instead of natural killer T cells, which may explain why corticosteroids fail to relieve symptoms in some patients. Since this was a preliminary study, Researchers will continue to look into the link between killer T cells and asthma.
Repetitious inflammation and asthma can actually cause permanent, irreversible damage to the functions and structures of the airways. This process of change is called remodeling and remodeled airways and can lead to chronic asthma.
Researchers have found two potential links between the body’s natural responses and remodeling. Interleukins 11 and 13, two immune compounds, may be responsible for some remodeling. These chemicals are involved with scarring and cellular growth in the smooth muscles of airways. Another link involves compounds known as growth factors. Vascular Endothelial Growth Factor (VEGF), a specific type of growth factor compound, promotes cellular growth in the linings of blood vessels and has been observed in the airways of asthma patients.