Cells And Organs Of Immune System Pdf


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The immune system includes primary lymphoid organs, secondary lymphatic tissues and various cells in the innate and adaptive immune systems. The key primary lymphoid organs of the immune system include the thymus and bone marrow, as well as secondary lymphatic tissues including spleen, tonsils, lymph vessels, lymph nodes, adenoids, skin, and liver.

Immunity in the Gut

The immune system is designed to defend the body against foreign or dangerous invaders. Such invaders include. Microorganisms commonly called germs, such as bacteria , viruses , and fungi.

Parasites such as worms. Antigens are any substances that the immune system can recognize and that can thus stimulate an immune response. If antigens are perceived as dangerous for example, if they can cause disease , they can stimulate an immune response in the body. Antigens may be contained within or on bacteria, viruses, other microorganisms, parasites, or cancer cells. Antigens may also exist on their own—for example, as food molecules or pollen. A normal immune response consists of the following:.

The body generates an immune response against itself an autoimmune disorder. The body cannot generate appropriate immune responses against invading microorganisms an immunodeficiency disorder.

The body generates an excessive immune response to often harmless foreign antigens and damages normal tissues an allergic reaction. Antibodies immunoglobulins are proteins that are produced by white blood cells called B cells and that tightly bind to the antigen of an invader, tagging the invader for attack or directly neutralizing it.

The body produces thousands of different antibodies. Each antibody is specific to a given antigen. Antigens are any substance that the immune system can recognize and that can thus stimulate an immune response. B cells B lymphocytes are white blood cells that produce antibodies specific to the antigen that stimulated their production.

Basophils are white blood cells that release histamine a substance involved in allergic reactions and that produce substances to attract other white blood cells neutrophils and eosinophils to a trouble spot. Cells are the smallest unit of a living organism, composed of a nucleus and cytoplasm surrounded by a membrane. Chemotaxis is the process of by which a chemical substance attracts cells to a particular site. The complement system consists of a group of proteins that are involved in a series of reactions called the complement cascade designed to defend the body—for example, by killing bacteria and other foreign cells, making foreign cells easier for macrophages to identify and ingest, and attracting macrophages and neutrophils to a trouble spot.

Dendritic cells are derived from white blood cells. They reside in tissues and help T cells recognize foreign antigens. Eosinophils are white blood cells that kill bacteria and other foreign cells too big to ingest, and they may help immobilize and kill parasites and help destroy cancer cells.

Eosinophils also participate in allergic reactions. Helper T cells are white blood cells that help B cells produce antibodies against foreign antigens, help killer T cells become active, and stimulate macrophages, enabling them to ingest infected or abnormal cells more efficiently. Histocompatibility literally, compatibility of tissue is determined by human leukocyte antigens self-identification molecules. Histocompatibility is used to determine whether a transplanted tissue or organ will be accepted by the recipient.

Human leukocyte antigens HLA are a group of identification molecules located on the surface of all cells in a combination that is almost unique for each person, thereby enabling the body to distinguish self from nonself. This group of identification molecules is also called the major histocompatibility complex. Interleukin is a type of messenger cytokine secreted by some white blood cells to affect other white blood cells.

Killer cytotoxic T cells are T cells that attach to infected cells and cancer cells and kill them. Leukocyte is another name for a white blood cell, such as a monocyte, a neutrophil, an eosinophil, a basophil, or a lymphocyte a B cell or T cell. The lymphatic system is a network of lymph nodes connected by lymphatic vessels that helps the body transport microorganisms and dead or damaged cells to be filtered out and destroyed. Acquired immune responses are initiated in the lymph nodes.

Lymphocytes are the white blood cells responsible for acquired specific immunity, including producing antibodies by B cells , distinguishing self from nonself by T cells , and killing infected cells and cancer cells by killer T cells. Macrophages are large cells that develop from white blood cells called monocytes. They ingest bacteria and other foreign cells and help T cells identify microorganisms and other foreign substances.

Macrophages are normally present in the lungs, skin, liver, and other tissues. Mast cells are cells in tissues that release histamine and other substances involved in inflammatory and allergic reactions. Natural killer cells are a type of white blood cell that can recognize and kill abnormal cells, such as certain infected cells and cancer cells, without having to first learn that the cells are abnormal.

Neutrophils are white blood cells that ingest and kill bacteria and other foreign cells. Phagocytes are a type of cell that ingests and kills or destroys invading microorganisms, other cells, and cell fragments.

Phagocytes include neutrophils and macrophages. Phagocytosis is the process of a cell engulfing and ingesting an invading microorganism, another cell, or a cell fragment.

T cells T lymphocytes are white blood cells that are involved in acquired immunity. There are three types: helper, killer cytotoxic , and regulatory.

White blood cells leukocytes exist in several different types, such as monocytes, neutrophils, eosinophils, basophils, and lymphocytes B cells and T cells , each of which have different roles in the immune system. As long as these barriers remain unbroken, many invaders cannot enter the body.

If a barrier is broken—for example, if extensive burns damage the skin—the risk of infection is increased. In addition, the barriers are defended by secretions containing enzymes that can destroy bacteria. Examples are sweat, tears in the eyes, mucus in the respiratory and digestive tracts, and secretions in the vagina.

The next line of defense involves white blood cells leukocytes that travel through the bloodstream and into tissues, searching for and attacking microorganisms and other invaders.

Innate natural immunity : Innate means something a person is born with. So innate immunity does not require a previous encounter with a microorganism or other invader to work effectively. It responds to invaders immediately, without needing to learn to recognize them.

Several types of white blood cells are involved:. Phagocytes ingest invaders. Phagocytes include macrophages , neutrophils , monocytes , and dendritic cells. Natural killer cells are formed ready to recognize and kill cancer cells and cells that are infected with certain viruses. Some white blood cells such as basophils and eosinophils release substances involved in inflammation , such as cytokines, and in allergic reactions, such as histamine. Some of these cells can destroy invaders directly.

Acquired adaptive or specific immunity : In acquired immunity, white blood cells called lymphocytes B cells and T cells encounter an invader, learn how to attack it, and remember the specific invader so that they can attack it even more efficiently the next time they encounter it.

Acquired immunity takes time to develop after the initial encounter with a new invader because the lymphocytes must adapt to it. However, thereafter, response is quick. B cells and T cells work together to destroy invaders.

To be able to recognize invaders, T cells need help from cells called antigen-presenting cells such as dendritic cells—see figure How T Cells Recognize Antigens. These cells ingest an invader and break it into fragments. Innate immunity and acquired immunity interact, influencing each other directly or through molecules that attract or activate other cells of the immune system—as part of the mobilization step in defense.

These molecules include. Cytokines which are the messengers of the immune system. Complement proteins which form the complement system. These substances are not contained in cells but are dissolved in a body fluid, such as plasma the liquid part of blood.

Inflammation occurs because these molecules attract immune system cells to the affected tissue. To help get these cells to the tissue, the body sends more blood to the tissue. To carry more blood to the tissue, blood vessels expand and become more porous, allowing more fluids and cells to leave blood vessels and enter the tissue. Inflammation thus tends to cause redness, warmth, and swelling. The purpose of inflammation is to contain the infection so that it does not spread. Then other substances produced by the immune system help the inflammation resolve and damaged tissues heal.

Although inflammation may be bothersome, it indicates that the immune system is doing its job. However, excessive or long-term chronic inflammation can be harmful. The immune system includes several organs in addition to cells dispersed throughout the body. These organs are classified as primary or secondary lymphoid organs.

The bone marrow produces all the different types of white blood cells, including neutrophils, eosinophils, basophils, monocytes, B cells, and the cells that develop into T cells T cell precursors.

T cells are critical for acquired immunity. When needed to defend the body, the white blood cells are mobilized, mainly from the bone marrow. They then move into the bloodstream and travel to wherever they are needed. The lymphatic system is a vital part of the immune system, along with the thymus, bone marrow, spleen, tonsils, appendix, and Peyer patches in the small intestine. The lymphatic system is a network of lymph nodes connected by lymphatic vessels.

This system transports lymph throughout the body. Lymph is formed from fluid that seeps through the thin walls of capillaries into the body's tissues. This fluid contains oxygen, proteins, and other nutrients that nourish the tissues. Some of this fluid reenters the capillaries and some of it enters the lymphatic vessels becoming lymph.

Small lymphatic vessels connect to larger ones and eventually form the thoracic duct. The thoracic duct is the largest lymphatic vessel. It joins with the subclavian vein and thus returns lymph to the bloodstream. Lymph also transports foreign substances such as bacteria , cancer cells, and dead or damaged cells that may be present in tissues into the lymphatic vessels and to lymph nodes for disposal. Lymph contains many white blood cells.

All substances transported by the lymph pass through at least one lymph node, where foreign substances can be filtered out and destroyed before fluid is returned to the bloodstream.

How the immune system works

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The adaptive immune system , also referred as the acquired immune system , is a subsystem of the immune system that is composed of specialized, systemic cells and processes that eliminate pathogens or prevent their growth. The acquired immune system is one of the two main immunity strategies found in vertebrates the other being the innate immune system. Like the innate system, the adaptive immune system includes both humoral immunity components and cell-mediated immunity components and destroys invading pathogens. Unlike the innate immune system , which is pre-programmed to react to common broad categories of pathogen, the adaptive immune system is highly specific to each particular pathogen the body has encountered. Adaptive immunity creates immunological memory after an initial response to a specific pathogen, and leads to an enhanced response to future encounters with that pathogen. Antibodies are a critical part of the adaptive immune system. Adaptive immunity can provide long-lasting protection, sometimes for the person's entire lifetime.

11.1A: Cells and Organs of the Immune System

The immune system is composed of a variety of different cell types and proteins. The immune system is a wonderful collaboration between cells and proteins that work together to provide defense against infection. These cells and proteins do not form a single organ like the heart or liver.

The immune system is designed to defend the body against foreign or dangerous invaders. Such invaders include. Microorganisms commonly called germs, such as bacteria , viruses , and fungi. Parasites such as worms. Antigens are any substances that the immune system can recognize and that can thus stimulate an immune response.

The immune system is designed to defend the body against foreign or dangerous invaders. Such invaders include. Microorganisms commonly called germs, such as bacteria , viruses , and fungi. Parasites such as worms.

The Immune System and Primary Immunodeficiency

Our immune system is essential for our survival. Without an immune system, our bodies would be open to attack from bacteria, viruses, parasites, and more. It is our immune system that keeps us healthy as we drift through a sea of pathogens.

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Immune System. • Cells. – Innate response- several cell types. – Adaptive (​specific) response- lymphocytes. • Organs. – Primary where.

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