Immune system

The immune system is a host defense system comprising many biological structures and processes within an organism that protects against disease.

For example, internal dysfunctions of the immune system can produce a variety of different diseases, including various forms of immunodeficiency, hypersensitivity, allergies and autoimmune disorders.

In humans, the blood–brain barrier, blood–cerebrospinal fluid barrier, and similar fluid–brain barriers separate the peripheral immune system from the neuroimmune system, which protects the brain.

The neuroimmune system is a system of structures and processes involving the biochemical and electrophysiological interactions between the nervous system and immune system which protect neurons from pathogens.

These mechanisms include phagocytosis, antimicrobial peptides called defensins, and the complement system.

The complement system is a part of the immune system that enhances (complements) the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism, promotes inflammation, and attacks the pathogen's cell membrane.

To function properly, an immune system must detect a wide variety of agents, known as pathogens, from viruses to parasitic worms, and distinguish them from the organism's own healthy tissue.

The presented antigen can be either self or non-self, thus preventing an organism's immune system targeting its own cells.

Immunodeficiency occurs when the immune system is less active than normal, resulting in recurring and life-threatening infections.

Immunodeficiency (or immune deficiency) is a state in which the immune system's ability to fight infectious disease and cancer is compromised or entirely absent.

This process of acquired immunity is the basis of vaccination.

Vaccination is the administration of antigenic material (a vaccine) to stimulate an individual's immune system to develop adaptive immunity to a pathogen.

Adaptive (or acquired) immunity creates immunological memory after an initial response to a specific pathogen, leading to an enhanced response to subsequent encounters with that same pathogen.

Immunological memory is the ability of the immune system to quickly and specifically recognize an antigen that the body has previously encountered and initiate a corresponding immune response.

Even simple unicellular organisms such as bacteria possess a rudimentary immune system in the form of enzymes that protect against bacteriophage infections.

The vast majority of the bacteria in the body are rendered harmless by the protective effects of the immune system, though many are beneficial, particularly in the gut flora.

In humans, immunodeficiency can either be the result of a genetic disease such as severe combined immunodeficiency, acquired conditions such as HIV/AIDS, or the use of immunosuppressive medication.

AIDS is a condition in humans in which progressive failure of the immune system allows life-threatening opportunistic infections and cancers to thrive.

In humans, immunodeficiency can either be the result of a genetic disease such as severe combined immunodeficiency, acquired conditions such as HIV/AIDS, or the use of immunosuppressive medication.

As the infection progresses, it interferes more with the immune system, increasing the risk of developing common infections such as tuberculosis, as well as other opportunistic infections, and tumors that rarely affect people who have working immune systems.

Common autoimmune diseases include Hashimoto's thyroiditis, rheumatoid arthritis, diabetes mellitus type 1, and systemic lupus erythematosus.

Systemic lupus erythematosus (SLE), also known simply as lupus, is an autoimmune disease in which the body's immune system mistakenly attacks healthy tissue in many parts of the body.

Disorders of the immune system can result in autoimmune diseases, inflammatory diseases and cancer.

A series of biochemical events propagates and matures the inflammatory response, involving the local vascular system, the immune system, and various cells within the injured tissue.

Immunology covers the study of all aspects of the immune system.

Immunology is a branch of biology that covers the study of immune systems in all organisms.

Common autoimmune diseases include Hashimoto's thyroiditis, rheumatoid arthritis, diabetes mellitus type 1, and systemic lupus erythematosus.

The underlying mechanism involves the body's immune system attacking the joints.

These mechanisms include phagocytosis, antimicrobial peptides called defensins, and the complement system.

Cells of the immune system contain these peptides to assist in killing phagocytosed bacteria, for example in neutrophil granulocytes and almost all epithelial cells.

These mechanisms include phagocytosis, antimicrobial peptides called defensins, and the complement system.

In an organism's immune system, phagocytosis is a major mechanism used to remove pathogens and cell debris.

It was not until Robert Koch's 1891 proofs, for which he was awarded a Nobel Prize in 1905, that microorganisms were confirmed as the cause of infectious disease.

Hosts can fight infections using their immune system.

This system does not confer long-lasting immunity against a pathogen.

Other components of the immune system adapt themselves to each new disease encountered and can generate pathogen-specific immunity.

In many species, the immune system can be classified into subsystems, such as the innate immune system versus the adaptive immune system, or humoral immunity versus cell-mediated immunity.

The study of the molecular and cellular components that form the immune system, including their function and interaction, is the central science of immunology.

As a result of the symbiotic relationship between commensals and the immune system, the probability that pathogens will reach sufficient numbers to cause illness is reduced.

The immune system is a host defense system consisting of anatomical barriers, and physiological and cellular responses, which protect the host against harmful parasites while limiting inflammation by tolerating harmless symbionts.

However, as organisms cannot be completely sealed from their environments, other systems act to protect body openings such as the lungs, intestines, and the genitourinary tract.

The gastrointestinal tract contains trillions of microbes, with some 4,000 different strains of bacteria having diverse roles in maintenance of immune health and metabolism.

Eicosanoids include prostaglandins that produce fever and the dilation of blood vessels associated with inflammation, and leukotrienes that attract certain white blood cells (leukocytes).

White blood cells (also called leukocytes or leucocytes and abbreviated as WBCs) are the cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders.

It originates from medicine and early studies on the causes of immunity to disease.

Immunology is the study of the immune system, which includes the innate and adaptive immune system in humans, for example.

Inflammation is produced by eicosanoids and cytokines, which are released by injured or infected cells.

Eicosanoids function in diverse physiological systems and pathological processes such as: mounting or inhibiting inflammation, allergy, fever and other immune responses; regulating the abortion of pregnancy and normal childbirth; contributing to the perception of pain; regulating cell growth; controlling blood pressure; and modulating the regional flow of blood to tissues.

The immune system is a host defense system comprising many biological structures and processes within an organism that protects against disease.

5) Defensive proteins, which can include everything from antibodies of the immune system, to toxins (e.g., dendrotoxins of snakes), to proteins that include unusual amino acids like canavanine