Mast cell

Tiny cells live in your body.

They act like little guards. These guards watch for things that might hurt you.

They look for germs or tiny bugs. When they find danger, they send out signals. This tells your body to help.

These signals can make your skin red or itchy. This happens when a bug bites you.

These cells also help fix your body. They help heal cuts and wounds. They have been around for a very long time.

Your body uses these guards to stay safe and well.

Mast cells are special white blood cells. They act like sentinels, or guards, for your body.

These cells live in your tissues. They stay near blood vessels and nerves. You can find them in your skin and lungs. They also live in your gut.

Mast cells have many small parts inside them. We call these parts granules. These granules hold chemicals like histamine.

When a mast cell finds danger, it lets these chemicals out. This can happen in two ways. It can let them out slowly. Or it can let them out very fast.

These chemicals help your body react. They can cause swelling or redness. They can also make you feel itchy. This is what happens after a mosquito bite.

Mast cells also help your body heal wounds. They help fight bacteria and viruses. Some people have allergies because of how mast cells work. These cells are very old. They have lived in animals for nearly 500 million years.

Mast cells are special white blood cells that act like sentinels for your body.

They live in connective and mucosal tissues to watch for danger. These cells stay near blood vessels, nerves, and lymphatic vessels. You can find them in your skin, lungs, and digestive tract. They also live in your mouth, nose, and even your brain. These cells help protect you from parasites, bacteria, viruses, and fungi. They even help your body respond to venoms.

These cells work by releasing tiny storage sacs called granules. These granules hold important chemicals like histamine and heparin. When a mast cell detects a signal of danger, it reacts. It can release these chemicals slowly through piecemeal degranulation. It can also release them very quickly during anaphylactic degranulation.

Once released, these chemicals help manage inflammation and repair. They can help heal wounds or help new blood vessels grow. This process helps your body return to a healthy state.

Scientists have studied these cells for a long time. Friedrich von Recklinghausen first described them in 1863. Later, Paul Ehrlich rediscovered them and gave them their name in 1877.

We now know these cells are very ancient. They likely started nearly 500 million years ago in urochordates. In humans, the very first mast cells begin to form in the yolk sac. This happens around three weeks into pregnancy. They then move into other tissues to finish growing.

There are many different types of mast cells. In humans, researchers found three main categories based on their proteins. One type is called MCT, which lives mostly in the small intestine. Another type is called MCTC, which is found in the skin and lymph nodes.

A third type is called MCC, which contains a protein called chymase. In mice, they are called connective tissue mast cells and mucosal mast cells. These different types have different physical and chemical traits. They are specialized for the specific place where they live.

You can see mast cells working in your daily life. Think about a mosquito bite on your arm.

When the cell detects the bite, it releases histamine. This chemical makes your blood vessels more permeable, which causes swelling. It also makes the area red, warm, and itchy. This is called a flare and wheal reaction. While this helps fight threats, it is also linked to allergies. This is why some people have eczema or strong allergic reactions.

Mast cells are specialized white blood cells that act as sentinels for the body.

They belong to the myeloid lineage and function within both the immune and neuroimmune systems. These cells reside in connective and mucosal tissues, often surrounding blood vessels, nerves, and lymphatic vessels. They are essential for detecting signals from parasites, pathogens, and other potential dangers. By managing inflammation and tissue repair, mast cells help maintain a healthy state. They play vital roles in wound healing, angiogenesis, and responding to bacteria, viruses, and fungi.

To perform their duties, mast cells use small secretory granules.

These granules store chemical mediators like histamine and heparin. When a mast cell detects a threat, it can release these substances in two ways. The first is piecemeal degranulation, which is a selective release of specific compounds. The second is anaphylactic degranulation, which is a rapid, large-scale release of mediators. Mast cells can also secrete newly synthesized mediators to manage long-term responses. This process allows the body to coordinate complex immune responses to various stimuli.

In humans, mast cells are categorized into three main types based on their protease expression.

The first type is MCT, which primarily resides in the mucosa of the lungs and small intestine. In fact, approximately 98% of mast cells in the human small intestine are MCT. The second type is MCTC, which is found in the skin, lymph nodes, and the submucosa of the gut. MCTC expresses tryptase, chymase, and carboxypeptidase. The third type is MCC, which expresses chymase but does not contain tryptase. These variations allow cells to be specialized for their specific environments.

In rodent models, the classification is slightly different. Researchers identify two major categories: connective tissue-resident mast cells (CTMCs) and mucosal mast cells (MMCs). CTMCs contain heparin and high amounts of histamine and carboxypeptidase. They are distributed in the skin and the peritoneal cavity. MMCs predominantly contain chondroitin sulfate and are found in the gastrointestinal tract. These different chemical profiles help the cells react appropriately to the specific threats found in different body locations.

The history of mast cell study began in the 19th century. Friedrich von Recklinghausen first described these cells in 1863. Later, in 1877, Paul Ehrlich rediscovered them and provided the name we use today. We now know that mast cells are among the most ancient immune cells. They likely originated nearly 500 million years ago in urochordates. This long history shows how fundamental these cells are to animal life.

The development of mast cells is a complex, multi-wave process. In humans, the first mast cells originate from mesodermal precursors in the yolk sac. This begins around three weeks into gestation. These progenitors then migrate into peripheral tissues to complete their maturation. While there is debate about whether adult mast cells come from bone marrow, many fetal-derived cells persist into adulthood. These cells often maintain themselves independently of the bone marrow.

Mast cell activity can be seen in common physical reactions. For example, a mosquito bite triggers a "flare and wheal" reaction. When the cell detects an allergen, it releases histamine. Histamine dilates blood vessels and increases permeability, causing redness, warmth, and swelling. It also depolarizes nerve endings, which causes itching or pain. While this helps fight threats, mast cell dysfunction is also linked to allergies, anaphylaxis, and atopic dermatitis.