Immunization

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Immunization

Immunization, or immunisation, is the process by which an individual's immune system

Immune system

An immune system is a collection of biological processes within an organism that protects against disease by identifying and killing pathogens and tumour cells....
becomes fortified against an agent (known as the immunogen

Antigen

An antigen is a substance that prompts the generation of antibodies and can cause an immune response. The word originated from the notion that they can stimulate antibody generation....
).

When an immune system is exposed to molecule

Molecule

In chemistry, a molecule is defined as a sufficiently stable, electric charge neutral group of at least two atoms in a definite arrangement held together by very strong chemical bonds....
s that are foreign to the body (non-self), it will orchestrate an immune response, but it can also develop the ability to quickly respond to a subsequent encounter (through immunological memory).

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Encyclopedia

Immunization, or immunisation, is the process by which an individual's immune system

Immune system

Antigen

Molecule

Adaptive immune system

The adaptive immune system is composed of highly specialized, systemic cells and processes that eliminate or prevent pathogenic challenges. Thought to have arisen in the first Gnathostomata, the adaptive or "specific" immune system is activated by the ?non-specific? and evolutionarily older innate immune system ....
. Therefore, by exposing an animal to an immunogen in a controlled way, their body can learn to protect itself: this is called active immunization.

The most important elements of the immune system that are improved by immunization are the B cell

B cell

B cells are lymphocytes that play a large role in the humoral immunity . The principal functions of B cells are to make antibody against antigens, perform the role of Antigen Presenting Cells and eventually develop into memory B cells after activation by antigen interaction....
s (and the antibodies

Antibody

Antibodies are gamma globulin proteins that are found in blood or other bodily fluids of vertebrates, and are used by the immune system to identify and neutralize foreign objects, such as bacterium and viruses....
they produce) and T cell

T cell

T cells belong to a group of white blood cells known as lymphocytes, and play a central role in cell-mediated immunity. They can be distinguished from other lymphocyte types, such as B cells and natural killer cells by the presence of a special receptor on their cell surface called T cell receptors ....
s. Memory B cell

Memory B cell

Memory B cells are a B cell sub-type that are formed following primary infection....
and memory T cells

Memory T cells

Memory T cells are a specific type of infection-fighting T cell that can recognize foreign invaders such as bacteria or viruses, that were encountered during a prior infection or vaccination....
are responsible for a swift response to a second encounter with a foreign molecule. Passive immunization is when these elements are introduced directly into the body, instead of when the body itself has to make these elements.

Immunization can be done through various techniques, most commonly vaccination
Vaccination

Vaccination is the administration of antigenic material to produce immunity to a disease. Vaccines can prevent or ameliorate the effects of infection by a pathogen....
. Vaccines against microorganism

Microorganism

A microorganism or microbe is an organism that is microscopic . The study of microorganisms is called microbiology, a subject that began with Anton van Leeuwenhoek's discovery of microorganisms in 1675, using a microscope of his own design....
s that cause disease

Disease

A disease or medical condition is an abnormal condition of an organism that impairs bodily functions, associated with specific symptoms and Medical signs....
s can prepare the body's immune system, thus helping to fight or prevent an infection

Infection

An infection is the detrimental colonization of a host organism by a foreign species. In an infection, the infecting organism seeks to utilize the host resources to multiply ....
. The fact that mutation

Mutation

In biology, mutations are changes to the nucleotide sequence of the genetic material of an organism. Mutations can be caused by copying errors in the genetic material during cell division, by exposure to ultraviolet or ionizing radiation, chemical mutagens, or virus , or can be induced by the organism, itself, by cellular processes such as s...
s can cause cancer

Cancer

Cancer is a class of diseases in which a group of cell display uncontrolled growth , invasion , and sometimes metastasis . These three malignant properties of cancers differentiate them from benign tumors, which are self-limited, do not invade or metastasize....
cells

Cell (biology)

The cell is the structural and functional unit of all known Life organisms. It is the smallest unit of an organism that is classified as living, and is often called the building bricks of life....
to produce proteins or other molecules that are unknown to the body forms the theoretical basis for therapeutic cancer vaccine

Cancer vaccine

The term cancer vaccine refers to a vaccine that either prevents infections with cancer-causing viruses, or treats existing cancer.Some cancers, such as cervical cancer and some Hepatocellular carcinoma, are caused by viruses, and traditional vaccines against those viruses, such as HPV vaccine and Hepatitis B vaccine, will prevent those can...
s. Other molecules can be used for immunization as well, for example in experimental vaccines against nicotine

Nicotine

Nicotine is an alkaloid found in the nightshade family of plants which constitutes approximately 0.6?3.0% of dry weight of tobacco, with biosynthesis taking place in the roots, and accumulating in the leaves....
(NicVAX

NicVAX

NicVAX is a nicotine conjugate vaccine intended to reduce or eliminate physical addiction to nicotine. According to the National Institute on Drug Abuse, NicVAX can potentially be used to inoculation against addiction....
) or the hormone ghrelin

Ghrelin

Ghrelin is a hormone produced mainly by P/D1 cells lining the fundus of the human stomach and epsilon cells of the pancreas that stimulates appetite....
(in experiments to create an obesity vaccine).

Passive and active immunization

Immunization can be achieved in an active or passive fashion: vaccination is an active form of immunization.

Active immunization

Active immunization entails the introduction of a foreign molecule into the body, which causes the body itself to generate immunity against the target. This immunity comes from the T cells and the B cells with their antibodies.

Active immunization can occur naturally when a person comes in contact with, for example, a microbe. If the person has not yet come into contact with the microbe and has no pre-made antibodies for defense (like in passive immunization), the person becomes immunized. The immune system will eventually create antibodies and other defenses against the microbe. The next time, the immune response against this microbe can be very efficient; this is the case in many of the childhood infections that a person only contracts once, but then is immune.

Artificial active immunization is where the microbe, or parts of it, are injected into the person before they are able to take it in naturally. If whole microbes are used, they are pre-treated. Depending on the type of disease, this technique also works with dead microbes, parts of the microbe, or treated toxins from the microbe.

Passive immunization

Passive immunization is where pre-made elements of the immune system are transferred to a person, and the body doesn't have to create these elements itself. Currently, antibodies can be used for passive immunization. This method of immunization begins to work very quickly, but it is short lasting, because the antibodies are naturally broken down, and if there are no B cells to produce more antibodies, they will disappear.

Passive immunization can be naturally acquired when antibodies are being transferred from mother to fetus

Fetus

A fetus is a developing mammal or other viviparous vertebrate, after the embryonic stage and before childbirth. The plural is fetuses, or sometimes feti....
during pregnancy

Pregnancy

Pregnancy is the carrying of one or more offspring, known as a fetus or embryo, inside the uterus of a female. In a pregnancy, there can be multiple gestations, as in the case of twins or Multiple birth....
, to help protect the fetus before and shortly after birth.

Artificial passive immunization is normally given by injection

Injection

Injection may refer to:* Injection , a method of putting liquid into the body with a syringe and a hollow needle that punctures the skin.* Injective function in mathematics, a function which associates distinct arguments to distinct values...
and is used if there has been a recent outbreak of a particular disease or as an emergency treatment to poisons (for example, for tetanus

Tetanus

Tetanus, also called lockjaw, is a medical condition characterized by a prolonged contraction of skeletal muscle fibers. The primary symptoms are caused by tetanospasmin, a neurotoxin produced by the Gram-positive, Anaerobic organism Clostridium tetani....
). The antibodies can be produced in animals or in vitro
In vitro

In vitro refers to the technique of performing a given procedure in a controlled environment outside of a living organism. Some may argue that in vitro refers to a process that is created in a "test tube"; however, Robert Kail and John Cavanaugh on page 58 in the 4th edition of Human Development: A Life-Span View cite that in fact th...
.

Immunization

Passive and active immunization

Active immunization

Passive immunization

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