Eosinophils are one of the white blood cell types that are quite unique from the rest of the white blood cells. They participate significantly in the immune system's activity. The cells were first found in the late 19th century. They were named after their affinity for eosin, a red dye used in microscopes. Eosinophils belong to granulocytes which further include neutrophils...
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As a rule these cells are bilobed with fine granules in their cytoplasm containing proteins that have extraordinary power in combating bacteria, viruses and other pathogens. In the circulation, the eosinophils are only about 1-4% of the total amount of white blood cells but their influence is crucial and very often it is complicated.
Under normal conditions, eosinophils explore the body, mainly tissues that border with the outer environment, such as the skin, lungs, and gastrointestinal tract. They are important not only in anthelmintic action but The point is that they also play an active role in allergy matter and tissue homeostasis. However, just like the other immune system constituents, if the levels of eosinophils are disordered, this can be related to all sorts of health challenges.
Eosinophils are the result of the differentiation and maturation of hematopoietic stem cells in the bone marrow. These are the same kind of cells that give rise to all other blood cells. In particular, the elicitations of various growth factors and cytokines, especially interleukin-5 (IL-5), have a big impact on the cell fate decision of these stem cells, leading them to mature eosinophils. After maturation, the eosinophils are, first, after being achieved with the synthesis in the bone marrow, released into the blood, where they remain for an extremely short time, i.e., from 8 to 12 hours, before they start penetrating into the tissues.
On a structural basis, eosinophils are a so-called segmented blood cell type that is defined by its horse shoe-like core in most microscope images and also their cytoplasm is prominent with specific granules which are loaden with cytotoxic proteins like major basic protein (MBP), eosinophil cationic protein (ECP), eosinophil peroxidase (EPO), and eosinophil-derived neurotoxin (EDN), to mention fewer. The inflammatory activity of these cells is materialized to a large degree by the presence of these granules.
Moreover, eosinophils are equipped with receptors on their surface that bind immunoglobulins as well as on the same cell type various chemokines, making it possible to relocate fast to the site of infection just, wherever it arises or any injury or inflammation. The phenomenon of degranulation through which the granules are being released transforms the eosinophils into both very efficient tissue modifiers and exposure agents, likewise to tissue damage if uncontrolled.
One of the primary roles of eosinophils is to act as a host of different immune system functions. It is sometimes a double-edged sword. Their major task is to defend the body from multicellular parasites, such as helminths. In these cases, the cells cover the worm, release their granules, and kill the parasite. This is not only the most important defense but also a necessary solution. It is especially true when parasitic infections regularly get out of control in some regions.
Another key role of eosinophils lies in the regulation of allergic responses. Eosinophils are major players in inflammation in diseases such as asthma and allergic rhinitis. They are responsible for the release of substances that can attract other immune cells, perpetuating the allergic response. Their granules can damage tissues, leading to the airway remodeling and hyperresponsiveness. These symptoms are observed in asthma.
They participate in the fight against the other cells in the parasite and are carriers of tissue health. Eosinophils release cytokines and growth factors. They are contributing to the whole process of organ development and wound healing, which, in turn, affects the behavior of the surrounding cells. It is the case that in some situations, they also have the job, in addition to the regulation of other aspects of the immune system, to promote a balanced response to the threat without causing too much damage to the tissue.
Conditions that may affect Eosinophils include the following:
Eosinophilic Esophagitis (EoE) is a kind of immune system, a chronic allergic disease where eosinophils gather in the esophagus. It causes inflammation and damage. Patients who have this disease (EoE) often go through the unpleasant feeling of being unable to swallow, food getting stuck in the throat, and chest pain that cannot be relieved by any regular medication for heartburn. Food allergens are believed to be the main cause of EoE. However, others link it to environmental allergens and sometimes to the environment. Continuous inflammation eventually causes fibrosis, which is when the esophagus gets too narrow. The common method of diagnosing is tissue biopsy by endoscopy, which shows a large number of eosinophils in the esophagus.
Hypereosinophilic Syndrome (HES) is a collection of very rare disorders characterized by a condition where eosinophil counts remain high without any apparent reason, such as parasitic infection or allergy. In HES, high levels of eosinophils can attack various organs, such as the heart, lungs, skin, and nervous system, and make them dysfunctional. Symptoms differ based on the affected organs. Still, they are usually intense and life-threatening. The main causes of HES may be primary (from the clone expansion of eosinophils) or secondary (due to the overproduction of eosinophil-promoting cytokines). The most common approach to the treatment, therefore, is corticosteroids or target therapies like tyrosine kinase inhibitors.
Eosinophilic Asthma is one of the subtypes of asthma with a characteristic of elevated levels of eosinophils in the airways. There is a difference between common asthma and eosinophilic asthma because it does not always necessarily need allergens as a trigger and still can even happen with no exposure to allergens. Furthermore, it is more severe and less responsive to the standard inhaled corticosteroids. Patients experience frequent chronic cough, exacerbations, and shortness of breath. The introduction of innovative biological therapies targeting IL-5 or its receptor has fostered hope for the control of very severe asthma of this type.
Eosinophilic Granulomatosis with Polyangiitis (EGPA), previously known as Churg-Strauss Syndrome, is a rare autoimmune condition. It initiates from asthma and is characterized by high levels of eosinophils and inflammation of blood vessels (vasculitis). EGPA could be generalized and present with a variety of symptoms of systemic vasculitis affecting different organs of the body such as acute sinusitis, neuropathy, skin lesion, and the heart. The exact cause has not yet been elucidated. Scientists claim that EGPA is the result of the complex interplay of an environmental trigger and immune dysregulation. Patients are mostly put on immunosuppressive therapy to ensure that no organ damage occurs.
Eosinophilic Pneumonia develops when eosinophils gather in the lung, making you cough, have shortness of breath, and have chest pain. The acute form of the disease is a medical emergency. It sets in quickly, often within a few days, and cries for immediate treatment. The chronic form of the disease is one that slowly develops. The symptoms mainly resemble other chronic lung diseases like asthma or interstitial lung diseases. Infections may be one of the causes, as well as drugs, allergens, or exposure to some other environmental hazards. But still, in a few cases, no clear reason is ever established.
When parasites, particularly helminths, cause infections, eosinophil numbers typically increase. The migration of eosinophils to sites of parasitic invasion is a normal defense mechanism of the body. The released granules contain toxic proteins against the parasites. However, the process can also affect host tissues. The major symptoms of eosinophilia are presented in the case of schistosomiasis, strongyloidiasis, and trichinosis. There are diseases where eosinophilia is the most known sign. Immigrants and travelers may have persistent eosinophilia that mandates further evaluation for parasitic etiologies.
Eosinophilic response, leading to the development of Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS) syndrome, may be caused by the intake of a few medicines. DRESS syndrome is a severe skin condition. It is characterized by a rash, fever, lymphadenopathy, and the involvement of internal organs like the liver and kidneys. There are many drugs that can be blamed for causing such syndrome. Among some of the culprits are antibiotics, anticonvulsants, and allopurinol. For the patient's chance of recovery, the illness must be recognized early, the drug that induced it should be withdrawn, and the patient should be treated with supportive care and corticosteroids.
Elevated eosinophil levels are often a result of allergic diseases. These include such conditions as atopic dermatitis, allergic rhinitis, and food allergies. Eosinophils play a role in tissue remodeling and chronic inflammation in these diseases. Locally for allergic skin parts, such as those with atopic dermatitis, eosinophils infiltrate these areas and release mediators which itch and also cause skin-barrier damage. In the case of the frequent fungi Alternaria and Cladosporium, the allergen-specific immune response against these antigens causes the eosinophils to recruit airway tissue.
There are many factors that cause the malfunctions of eosinophils that range from the complex and various often including genetic, environmental, and immunological ones. One of the examples is a genetic defect that triggers the bone marrow to produce too many eosinophils which is one of the forms of hypereosinophilic syndrome. Conversely, other scenarios suggest that the excessive production of eosinophil-promoting cytokines like IL-5 would cause secondary eosinophilia.
Parasitic infections, allergens, and some drugs can be environmental causes that may trigger the production of eosinophils. Infection is a natural boost to the eosinophil production as it is a defense mechanism. Then allergens can recruit the eosinophils as their part in an abundance of immune responses. On the other hand, drugs can unwantedly, impact on the immune system inappropriately, leading to eosinophil activation.
Autoimmune mechanisms are the most remarkable contributors and the disease that reflects it the most is EGPA. In these diseases, the immune system makes a mistake by attacking the animal's blood cells and tissues leading to eosinophil activation and storage. There are also rare instances where the specific cause of the disease is unclear. Such instances are called idiopathic eosinophilia which makes treatment more challenging.
For the majority of eosinophilic disorders, the issue is not only about the count of eosinophils but also includes their state of activation. Even the cells that are activated in a small number can get the damage done by releasing their granules in an uneven manner.
Keeping eosinophils healthy is directly related to the overall immune system balance. People should take care of the latter to make sure the former are in good condition. Eosinophils are able to detect and fight infections, allergens, and inflammation. Therefore, a careful lifestyle mode, which minimizes unnecessary immune activation, can be a big booster. Eating the two-pronged diet with all four food groups (fruits, vegetables, whole grains, and clean proteins) can provide the body with the necessary minerals and vitamins to manage cells of the immune system. A classic example of these vitamins is the Omega-3 fatty acids that can be found in both fish and flaxseed, and they are well-known for their anti-inflammatory features.
Next, the ability to manage stress is critical. The immune system can be shattered by chronic stress. It may result in setting the stage for inflammatory diseases where eosinophils will be apart. Physical exercise, meditation, deep breathing, plus enough sleep each night are the tactics that not only help you keep your immune system under control but also reduce the risk of getting sick. If you have an allergy, you must avoid allergens to be safe. Once you are exposed to allergens, your eosinophil numbers will go up in an instant, and this irritation phase could last for a long time, depending on the severity of the tissue's damage.
