Immunology

Your body has a way to stay well.

It has a special system to fight bad things. This system uses tiny cells to stay strong. Some cells work to find and eat bad things.

Other cells make tiny tools to mark targets. These tools help the body fight germs. This helps you stay healthy every day.

Immunology is the study of immune systems. These systems help all living things stay healthy.

Scientists look at how these systems work. They also study what happens when they fail. Some people have immune deficiency. This means their system is too weak. Others have autoimmune diseases. This is when the system attacks the body's own parts.

An antigen is a substance that starts a response.

Lymphocytes are cells that find these antigens. Once they find one, they make antibodies. Antibodies are proteins that mark targets. They do not kill germs directly. Instead, they show other cells where to go. Other cells, like phagocytes, then destroy the target.

Many organs help this work. These include the spleen and tonsils. The bone marrow and thymus also help. Some parts of the system move through the body. Others stay in specific tissues.

Doctors use this science to treat people. This is called immunotherapy. It can help with allergies or cancer. It can also help people who need organ transplants. This helps the body accept the new part.

Immunology is the study of how immune systems work in all living things. This science looks at how bodies stay healthy and how they fight disease. It also studies what happens when these systems do not work correctly. Sometimes, the system is too weak, which is called an immune deficiency. Other times, the system attacks the body's own parts in autoimmune diseases. Scientists study these systems in many ways, even looking at them in a lab.

How does the system actually work to protect you? It starts when it finds an antigen. An antigen is a substance that starts an immune response. Special cells called lymphocytes find these antigens. Once they find one, they make proteins called antibodies. These antibodies do not kill germs directly. Instead, they mark the germs so other cells, like phagocytes, can find and destroy them. This way, the body can recognize the difference between "self" and "non-self" parts.

People have noticed how immunity works for a very long time. In 430 BCE, a writer named Thucydides saw that people who survived the plague of Athens could nurse the sick without getting sick again. In the early 1900s, Ilya Mechnikov won a Nobel Prize for his work. He noticed cells moving to surround thorns in starfish larvae. This showed him how bodies defend themselves. Another scientist, Paul Ehrlich, found that mice could become "ricin-proof" after small doses of poison. This helped people understand how immunization works.

Many different parts of the body help the immune system function. Some are specific organs, like the thymus, bone marrow, and the spleen. Other parts include the tonsils, lymph nodes, and the liver. There are also lymph vessels that carry things through the body. Some immune parts are cells that travel through various tissues. Even babies have different immune levels than adults. A newborn's level of a protein called C3 is only about 65% of an adult's level.

Today, doctors use immunology to help people in many ways. One way is called immunotherapy, which uses the immune system to treat diseases. This can help with allergies, certain cancers, or autoimmune disorders like rheumatoid arthritis. It is also used to help people who receive organ transplants. This helps the body avoid transplant rejection. Doctors also use antibodies as tools to find different substances in the body. This makes immunology a very important part of modern medicine.

Immunology is a specialized branch of biology and medicine. It focuses on the study of immune systems in all living organisms. This science investigates how physiological functions work during both health and disease. Researchers also study what happens when these systems malfunction. These malfunctions can lead to immunological disorders. Examples include autoimmune diseases, hypersensitivities, and immune deficiencies. It also includes the study of transplant rejection. Scientists examine the physical and chemical characteristics of immune components in many different settings. They study them in living organisms, in specific places, and in laboratory environments.

The immune system operates through complex biological mechanisms. A central part of this process is the ability to distinguish between "self" and "non-self." The process begins when an antigen is detected. An antigen is any substance that triggers an immune response. Special cells known as lymphocytes are responsible for recognizing these antigens. Once they identify an antigen, these cells secrete antibodies. Antibodies are specific proteins that serve a vital purpose. They do not kill pathogens, such as microorganisms, directly. Instead, they neutralize them by marking them as targets. This allows other cells, such as phagocytes or NK cells, to find and destroy the threat. This specific interaction is known as the antibody response.

Scientists divide the immune system into two main categories. The first is the innate immune system, which is considered more primitive. The second is the acquired, or adaptive, immune system found in vertebrates. The adaptive system is further divided into two distinct parts. One part is the humoral component, which involves antibodies. The other part is the cell-mediated component. These systems rely on various lymphoid organs to function. Important organs include the thymus and the bone marrow. Other essential tissues include the spleen, tonsils, and lymph nodes. The liver and various lymph vessels also play major roles. Many immune components are cellular and circulate through many different tissues.

History shows that humans have observed immunity for centuries. The earliest written mention dates back to 430 BCE during the plague of Athens. The writer Thucydides noted that survivors could nurse the sick without getting sick again. However, it took until the 19th and 20th centuries to develop scientific theories. Ilya Ilyich Mechnikov was a Russian biologist who advanced this field greatly. He observed starfish larvae reacting to small thorns. He saw unusual cells surrounding the thorns to maintain the organism's integrity. This phenomenon is called phagocytosis. Mechnikov received the Nobel Prize in 1908 for his work. He shared this honor with Paul Ehrlich. Ehrlich studied how mice could become "ricin-proof" after small, increasing doses of poison. He interpreted this as a form of immunization.

Clinical immunology focuses on diseases caused by immune system disorders. These disorders generally fall into two broad categories. The first is immunodeficiency. This occurs when the system fails to provide an adequate response. Examples include primary immune diseases and chronic granulomatous disease. The second category is autoimmunity. This happens when the immune system attacks the body's own host. Examples include systemic lupus erythematosus and rheumatoid arthritis. It also includes Hashimoto's disease and myasthenia gravis. Another type of disorder is hypersensitivity. This involves inappropriate responses to harmless compounds, such as in asthma. A well-known immunodeficiency is AIDS. This disease is caused by HIV, which suppresses CD4+ T cells, dendritic cells, and macrophages.

Immunology has massive significance in modern medical practice. It is applied in fields like oncology, virology, and dermatology. It is also vital for organ transplantation to prevent rejection. Doctors use diagnostic immunology to detect substances in the body. They do this by attaching antibodies to fluorescent labels or enzymes. This allows them to find specific antigens. Another major application is immunotherapy. This uses immune components to treat diseases like cancer or allergies. It also helps patients who are immunosuppressed, such as those living with HIV. Research in this field drives advancements in biotechnology and biomedical research.

Developmental immunology shows how the system changes with age. Neonates, or newborns, exist in a state of physiological immunodeficiency. Their innate and adaptive responses are greatly suppressed at birth. For example, a newborn's level of C3 is only about 65% of an adult's level. Their phagocytic activity is also limited. This is due to lower opsonic activity and slower monocytes. While newborns have many lymphocytes, their cellular and humoral immunity is impaired. They rely on maternal factors for protection. Most of the immunoglobulin at birth is maternal IgG. This is transferred from the placenta via the FcRn receptor. Some IgA is also provided through breast milk. These antibodies can protect a newborn for up to 18 months.