Dendritic cell

Tiny cells help keep you healthy.

These cells act like little messengers. They live in your skin. They also live in your nose and lungs.

These cells look like small trees. They find germs in your body. Then they show the germs to other cells. This tells your body to fight. This keeps you strong and well.

Dendritic cells are special parts of your immune system. They act as messengers between different parts of your body's defense. These cells live in places that touch the outside world. You can find them in your skin, nose, lungs, and stomach.

These cells get their name from a Greek word for tree. This is because they grow long, branching parts called dendrites. These branches help the cell have a very large surface. This large surface helps them catch things in their environment.

Immature dendritic cells watch for germs like bacteria or viruses. They use special tools to find these tiny invaders. When they find a germ, they eat it. They break the germ into small pieces. Then, the cell moves to a lymph node. There, it shows the pieces to T cells. This process tells the T cells to start a fight. This helps your body respond to the germ. Scientists like Ralph Steinman won a Nobel Prize for this work. He helped us learn how these cells shape our immune response.

Dendritic cells are vital messengers in the mammalian immune system. They act as a bridge between two different defense systems. One system is called the innate immune system. The other is the adaptive immune system. These cells are found in places that touch the outside world. You can find them in your skin. They also live in the lining of your nose, lungs, stomach, and intestines.

These cells work through a very specific way it works. First, immature dendritic cells sample the area around them. They look for germs like viruses or bacteria. They use special tools called pattern recognition receptors to find these invaders. When they find a germ, they eat it. They break the germ into tiny pieces. This is called processing the antigen material. Once they do this, the cells become mature. They then move to a lymph node to show these pieces to T cells and B cells.

Scientists have spent a long time learning about these cells. Paul Langerhans first described them in the late nineteenth century. Because of him, they are sometimes called Langerhans cells. Later, Ralph M. Steinman and Zanvil A. Cohn created the name dendritic cells in 1973. Steinman did such important work that he won a Nobel Prize in 2011. He was honored for showing how these cells lead the adaptive immune response.

There are different types of these cells with unique jobs. Conventional dendritic cells are one type. They can help stimulate different kinds of T cells. Another type is the plasmacytoid dendritic cell. These cells can produce large amounts of a substance called interferon-alpha. In the blood, scientists can identify three specific types of these cells. They use special markers to tell them apart. For example, human blood has CD1c+ myeloid cells and CD303+ plasmacytoid cells.

Their name comes from a Greek word, déndron, which means tree. This describes the long, branching parts they grow. These branches are called dendrites. These structures give the cell a very large surface area. This large surface helps them interact with many other cells at once. They use these branches to touch and signal to other parts of the immune system. It is much like how a tree's wide branches reach out into the air.

Dendritic cells (DCs) are specialized antigen-presenting cells within the mammalian immune system. They function as essential messengers that bridge the innate and adaptive immune systems. By processing antigen material, they present it on their cell surfaces to T cells. This process allows the immune system to recognize and respond to specific invaders. Because they act as a link, they are vital for initiating a targeted defense. They are primarily located in tissues that contact the external environment. This includes the skin and the inner linings of the nose, lungs, stomach, and intestines.

The life cycle of a dendritic cell begins in the bone marrow. They are derived from hematopoietic stem cells (HSC), which are the body's primary blood-forming cells. These stem cells transform into immature dendritic cells. Immature cells have high endocytic activity, meaning they are very good at taking in materials. They use pattern recognition receptors (PRRs), such as toll-like receptors (TLRs), to sample the environment. These receptors recognize specific chemical signatures found on pathogens like bacteria or viruses. Sometimes, these cells even perform "nibbling," where they take in small pieces of membrane from live host cells.

Once an immature dendritic cell encounters a presentable antigen, it undergoes a major change. It becomes an activated, mature dendritic cell and begins to migrate. The cell upregulates a receptor called CCR7. This receptor acts like a compass, inducing the cell to travel through the blood or lymphatic system. The cell moves toward a lymph node or the spleen. During this transition, the cell breaks down pathogens into small protein fragments. It then displays these fragments on its surface using MHC molecules. The cell also increases its surface receptors, such as CD80, CD86, and CD40. These act as co-receptors to help activate T cells effectively.

There are several distinct types of dendritic cells defined by their structure and function. Conventional dendritic cells (cDCs), also known as myeloid dendritic cells, are very common. They are similar to monocytes and include subsets like cDC-1 and cDC-2. The cDC-1 subset is a major stimulator of cytotoxic T cells. The cDC-2 subset helps stimulate helper T cells. Another major type is the plasmacytoid dendritic cell (pDC). These cells look like plasma cells but share traits with myeloid cells. They are known for producing high amounts of interferon-alpha, a protein used in immune signaling. In human blood, scientists identify three specific types: CD1c+ myeloid DCs, CD141+ myeloid DCs, and CD303+ plasmacytoid DCs.

Beyond these, there are follicular dendritic cells (FDCs). These are found in lymphoid follicles and have long, branching processes. Unlike other DCs, FDCs likely come from mesenchymal origin rather than hematopoietic origin. They also do not express MHC class II molecules. The name "dendritic" comes from the Greek word *dendron*, meaning tree. This refers to the branched projections called dendrites. This structure gives the cell a very large surface-to-volume ratio. This high surface area allows the cell to interact with many other cells at once.

The history of these cells is tied to several important scientific discoveries. Paul Langerhans first described these cells in the late nineteenth century. Because of his work, they are often called Langerhans cells. In 1973, Ralph M. Steinman and Zanvil A. Cohn coined the term "dendritic cells." Steinman's research was so significant that it earned him the Nobel Prize in Physiology or Medicine in 2011. He was recognized for proving the central role these cells play in the adaptive immune response. Before the year 2000, researchers struggled to isolate them. They often had to use a "cocktail" of different antigens to find them.

Understanding dendritic cells is vital for medical science. For example, a rare myeloid cancer called blastic plasmacytoid dendritic cell neoplasm can occur. In this disease, malignant pDCs infiltrate tissues like the skin, bone marrow, and central nervous system. This can cause skin lesions or swollen lymph nodes. Additionally, certain viruses like HIV can bind to dendritic cells through receptors like DC-SIGN. In mice, these cells are replenished from the blood at a rate of 4,000 cells per hour. This constant renewal ensures the immune system remains ready to respond to new threats.