Cytokine

Tiny parts in your body talk.

They send messages to your cells. These messages help you stay well. They help fight germs. They also help you grow.

These parts work like a signal. They touch the outside of a cell. This tells the cell what to do. They can talk to cells nearby. They can even talk to cells far away. This helps your whole body stay strong.

Your body uses tiny messengers called cytokines. These are small proteins that help cells talk to each other.

Many different cells make them. This includes cells in your immune system.

Cytokines work by sending signals. They are usually too big to go inside a cell. Instead, they land on a receptor. A receptor is a special part on the cell surface. When a cytokine hits a receptor, it starts a chain of changes inside the cell. This tells the cell how to act.

These messengers are very important for your health. They help your body fight germs. They also help with inflammation, which is how your body reacts to injury. Some cytokines can even help a tiny embryo grow.

Cytokines can send messages in different ways. They can talk to the cell that made them. They can talk to cells nearby. They can even send signals to cells far away in the body. This helps your whole body work together to stay well.

Cytokines are tiny proteins that act as messengers for your body.

They are very important for cell signaling, which is how cells talk to each other. Many different types of cells make these proteins. This includes your immune cells and cells in your connective tissue. Some cytokines can even help a tiny embryo grow during development. They play a big part in how your body stays healthy and strong.

These messengers work through a very specific way of working. Most cytokines are too large to enter a cell directly. Instead, they land on a cytokine receptor on the cell surface. A receptor is like a special lock that only a specific cytokine can open. Once the cytokine hits the receptor, it starts a chain of changes inside. This process is called signaling, and it tells the cell what to do. It might tell a cell to grow or to fight a germ.

The name for these proteins comes from ancient Greek words. The word "cyto" means cell, and "kines" means movement. Scientists used to group them by which cells made them. They used names like lymphokines for cells called lymphocytes. They also used the name interleukins for signals sent to white blood cells. Today, scientists know these groups overlap quite a bit. This makes the study of cytokines very complex and interesting.

There are many different kinds of cytokines with unique jobs. Some belong to the four-alpha-helix bundle family, which is a large group. This group includes things like erythropoietin, which helps your body make blood cells. Other cytokines, like interferons, help your body fight off viruses. Some cytokines are pro-inflammatory, which helps with swelling and healing. Others are anti-inflammatory, which helps calm the body down. They work together to keep your body in balance.

Cytokines are different from the hormones in your body. Hormones usually come from specific glands, like the pancreas. However, almost all cells can make cytokines. Hormones also travel in much higher amounts than cytokines do. A cytokine like IL-6 can increase its amount 1,000 times during an infection. This helps your body react quickly to a hard job like fighting germs.

Cytokines are a broad category of small proteins that facilitate cell signaling. These proteins typically weigh between 5 and 25 kDa. They are essential for regulating many biological processes. They act as messengers that allow cells to communicate. A wide variety of cells produce them. This includes immune cells, endothelial cells, and fibroblasts. Some connective tissue cells also produce cytokines.

Most cytokines function through a specific interaction with target cells. They are usually too large to cross a cell membrane. Instead, they bind to specific cytokine receptors on the cell surface. This binding triggers a cascade of intracellular signaling. These signals can change how a cell functions. They might turn certain genes on or off. This process can result in the production of more cytokines. It can also change the number of receptors on a cell surface. This creates a complex web of communication within the body.

Cytokines can signal in three distinct ways. In autocrine signaling, a cell sends a signal to itself. In paracrine signaling, the signal travels to nearby cells. In endocrine signaling, the cytokine acts as a pyrogen to affect cells throughout the body.

This flexibility allows them to manage both local and systemic responses. They help maintain the balance between humoral and cell-based immune responses. They also regulate how specific cell populations grow and mature.

Scientists categorize cytokines in different ways. One method is based on their three-dimensional structure. The four-alpha-helix bundle family is one such group. This is a large family containing the IL-2 subfamily. This subfamily includes non-immunological cytokines like erythropoietin (EPO) and thrombopoietin (TPO). Another structural group is the cysteine knot cytokines. This group includes the transforming growth factor beta superfamily. Other groups include the IL-17 family and the interferon (IFN) subfamily.

Another way to classify them is by their function in the immune system. Type 1 cytokines, such as TNF and IFN-gamma, enhance cellular immune responses. Type 2 cytokines, such as IL-4 and IL-10, enhance antibody responses. These two groups often inhibit one another. If this balance is lost, it can lead to autoimmune disorders. Some cytokines are pro-inflammatory, which helps trigger responses like fever. Others are anti-inflammatory and help regulate the pathway to prevent damage.

Cytokines differ from classic hormones in several ways. Hormones are usually secreted from specific glands like the pancreas. In contrast, almost all nucleated cells can produce cytokines. Hormones also circulate in much higher concentrations. Classic hormones often stay within one order of magnitude. Some cytokines, like IL-6, circulate in picomolar concentrations. However, these levels can increase up to 1,000 times during infection or trauma.

Historically, the names for these proteins were based on where they came from. The term "interleukin" was once used for cytokines targeting white blood cells. "Lymphokines" referred to those produced by lymphocytes. "Chemokines" are those that mediate chemotaxis, which is cell movement. Today, these distinctions are considered obsolete. This is because cytokines show great redundancy and pleiotropism. This means many different cytokines can perform similar or multiple functions.

Cytokines are vital for many stages of life. During embryonic development, they help with embryo implantation and growth. They are also linked to aging. Dysregulated secretion in older populations can lead to "inflammaging." This may increase vulnerability to diseases like type 2 diabetes. Even specific conditions like narcolepsy have been linked to cytokine levels. A 2024 study found a correlation between IL-2 and fatigue in type 1 narcolepsy patients.