Eosinophil

Tiny cells live in your blood.

They are part of your body's defense. These cells fight tiny worms and some bugs.

They also help with allergies and asthma. They can make it hard to breathe. This happens when too many cells gather in the lungs.

These cells start in your bone marrow. Then they move into your blood. They can live in your body for many days.

Scientists use red dye to see them. The dye makes the cells look brick-red. This helps doctors find them under a microscope.

These small cells help keep you safe.

They work hard every single day.

Eosinophils are a special kind of white blood cell.

They help your body fight off parasites like worms. They also help control allergies and asthma.

These cells start in your bone marrow. This is the soft part inside your bones. They grow there before moving into your blood. Once they are ready, they do not make more of themselves. They move into your tissues to work.

Scientists call them eosinophils because they love acid.

When scientists use a red dye called eosin, the cells turn brick-red. This happens because of tiny parts inside them called granules. These granules hold many chemicals.

When an eosinophil finds a germ, it uses a way called degranulation. This is when the cell lets out its chemicals to fight. These chemicals can be toxic to parasites. However, they can also hurt your own body. This is why too many eosinophils can cause swelling. In people with asthma, these cells can damage lung tissue. This makes it much harder to breathe.

Cells like these stay in your blood for about 12 hours. They can live in your tissues for up to 12 days.

Eosinophils are a special type of white blood cell. They are part of your immune system. Their main job is to fight multicellular parasites, like worms. They also play a role in fighting some viral infections. Along with other cells, they help control allergies and asthma.

In a healthy person, they make up 1% to 3% of all white blood cells. They are about 12 to 17 micrometres in size. They also have a nucleus with two lobes.

These cells follow a specific way of working. They start as precursor cells in the bone marrow. A signal called interleukin-5 helps them develop there. Once they are fully grown, they move into your blood. They do not multiply once they reach this stage.

After moving through the blood, they live in your tissues. They can stay in the blood for 8 to 12 hours. In your tissues, they can survive for 8 to 12 days.

Scientists call these cells eosinophils because they are "acid-loving." This name comes from how they react to certain dyes. Inside the cell are tiny parts called granules. These granules love acid. When scientists use a red dye called eosin, the granules soak it up. This makes the cells look brick-red under a microscope.

These granules hold many different chemicals to help the cell fight.

When an eosinophil is activated, it uses a process called degranulation. This is when the cell releases its granules to attack a target. The granules contain many different things like major basic protein. They also contain eosinophil peroxidase and several enzymes. These chemicals are toxic to parasites. However, they can also be toxic to your own body. This can cause inflammation and damage to your tissues.

Too many eosinophils can lead to health problems. Having more than 500 cells per microliter is called eosinophilia. This often happens during an allergic reaction or an asthma attack. In asthma, these cells can build up in the lungs. This causes swelling and makes it hard to breathe.

Doctors can use blood counts to help choose the right medicine. Some medicines help stop these cells from growing or working too much.

Eosinophils are a specialized type of white blood cell within the vertebrate immune system. They belong to a group of cells known as granulocytes. These cells are essential for combating multicellular parasites, such as helminths, which are parasitic worms. Eosinophils also play a role in fighting certain viral infections. Beyond fighting invaders, they work alongside mast cells and basophils to manage allergic responses and asthma.

The development of an eosinophil is a precise biological process. It begins during hematopoiesis, which is the production of blood cells in the bone marrow. Myeloid precursor cells begin to differentiate into eosinophils under the influence of specific signals. One critical signal is interleukin-5 (IL-5), a cytokine that controls their development. Other transcription factors, such as GATA and C/EBP, help determine their lineage fate. During this maturation, the cells produce and store many secondary granule proteins. Once they have reached terminal differentiation, they migrate into the bloodstream and can no longer multiply.

Eosinophils are named for their unique reaction to acidic dyes. They are "acidophilic," or acid-loving, because their cytoplasm contains large granules with a high affinity for acids. When scientists use the Romanowsky method to stain cells, they apply a red dye called eosin. The granules soak up this dye, making the cells appear brick-red under a microscope.

These cells typically measure between 12 and 17 micrometres in size. They are also characterized by having a bilobed nucleus, meaning the nucleus has two distinct parts.

Once mature, eosinophils move from the blood into various tissues throughout the body. They reside in several specific locations, including the spleen, lymph nodes, ovaries, uterus, and the prostate. They are also found in the thymus, specifically in the medulla and the junction between the cortex and medulla. In a healthy state, they are generally not found in the skin, lungs, or esophagus. Eosinophils persist in the circulation for about 8 to 12 hours. However, they can survive in tissues for an additional 8 to 12 days if they are not stimulated.

The primary way eosinophils fight infections is through a process called degranulation. When an eosinophil is activated by an immune stimulus, it releases the chemical mediators stored in its granules. This process can also involve cytolysis, where the cell breaks apart to release granules within extracellular DNA traps. These granules contain many toxic substances, such as major basic protein (MBP), eosinophil peroxidase (EPX), and eosinophil cationic protein (ECP). These proteins are designed to kill parasites, but they are also toxic to the host's own tissues. For example, ECP can create toxic pores in cell membranes, while EPX can cause oxidative stress that leads to cell death through apoptosis or necrosis.

Because these cells can cause tissue damage, their numbers must be carefully regulated. In a healthy individual, eosinophils make up only about 1% to 3% of all white blood cells. The median blood eosinophil count for healthy adults is approximately 100 cells/μL. If the count rises above 500 cells per microliter, the condition is called eosinophilia.

Eosinophilia can be caused by parasitic infestations, autoimmune diseases like systemic lupus erythematosus, or allergic conditions. In asthma, high levels of eosinophils lead to inflammation and airway remodeling, which makes breathing difficult.

Medical science has made significant progress in understanding and treating eosinophil-related issues. In the 1980s, pioneering research showed that eosinophils were unique because they could survive for long periods after maturation. Today, doctors use blood counts to predict how well certain drugs will work. Some treatments, like corticosteroids, promote apoptosis to reduce cell numbers. Other advanced therapies use monoclonal antibodies. For instance, mepolizumab and benralizumab target the IL-5 receptor to stop eosinophils from developing or to eliminate them through antibody-dependent cell-mediated cytotoxicity. Other drugs like dupilumab target IL-13 to reduce the inflammation caused by these cells.