Immunity (medical)

immunityimmuneimmune responseimmune memoryartificially acquired immunityimmune capacityimmune functionimmune functionsImmune responsesimmune system
In biology, immunity is the balanced state of multicellular organisms having adequate biological defenses to fight infection, disease, or other unwanted biological invasion, while having adequate tolerance to avoid allergy, and autoimmune diseases.wikipedia
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Adaptive immune system

adaptive immunityadaptive immune responseadaptive
An immune system may contain innate and adaptive components.
The acquired immune system is one of the two main immunity strategies found in vertebrates (the other being the innate immune system).

Artificial induction of immunity

induced immunityinducing immunitydeliberate actions
Adaptive immunity can be sub-divided depending on how the immunity was introduced in 'naturally acquired' through chance contact with a disease-causing agent, whereas 'artificially acquired immunity' develops through deliberate actions such as vaccination.
Immunity against infections that can cause serious illness is generally beneficial.

Humoral immunity

humoralhumoral immune responsehumoral response
Adaptive immunity can also be divided by the type of immune mediators involved; humoral immunity is the aspect of immunity that is mediated by secreted antibodies, whereas cell mediated immunity involves T-lymphocytes alone.
Humoral immunity or humoural immunity is the aspect of immunity that is mediated by macromolecules found in extracellular fluids such as secreted antibodies, complement proteins, and certain antimicrobial peptides.

Immune system

immuneimmune responseimmune responses
Other components of the immune system adapt themselves to each new disease encountered and can generate pathogen-specific immunity. Passive immunity can occur naturally, when maternal antibodies are transferred to the foetus through the placenta, and can also be induced artificially, when high levels of human (or horse) antibodies specific for a pathogen or toxin are transferred to non-immune individuals.
This system does not confer long-lasting immunity against a pathogen.

Lymphocyte

lymphocyteslymphocyticlymphoid
The adaptive system is composed of more advanced lymphatic cells that are programmed to recognise self-substances and don't react.
Throughout the lifetime of an animal, these memory cells will "remember" each specific pathogen encountered, and are able to mount a strong and rapid response if the same pathogen is detected again; this is known as acquired immunity.

Immunology

immunologistimmunologicalimmunologic
With Louis Pasteur's germ theory of disease, the fledgling science of immunology began to explain how bacteria caused disease, and how, following infection, the human body gained the ability to resist further infections.
Prior to the designation of immunity, from the etymological root immunis, which is Latin for "exempt", early physicians characterized organs that would later be proven as essential components of the immune system.

Infection

infectious diseaseinfectious diseasesinfectious
In biology, immunity is the balanced state of multicellular organisms having adequate biological defenses to fight infection, disease, or other unwanted biological invasion, while having adequate tolerance to avoid allergy, and autoimmune diseases.
Specific acquired immunity against infectious diseases may be mediated by antibodies and/or T lymphocytes.

Louis Pasteur

PasteurPasteur, LouisPasteurian
With Louis Pasteur's germ theory of disease, the fledgling science of immunology began to explain how bacteria caused disease, and how, following infection, the human body gained the ability to resist further infections.
Upon reusing these healthy chickens, Pasteur discovered he could not infect them, even with fresh bacteria; the weakened bacteria had caused the chickens to become immune to the disease, though they had caused only mild symptoms.

Vaccination

vaccinationsvaccinatedvaccinating
By 1800 the procedure was referred to as vaccination.
Vaccination is the administration of antigenic material (a vaccine) to stimulate an individual's immune system to develop adaptive immunity to a pathogen.

Polio vaccine

oral polio vaccinepolio vaccinationpolio
In 1891, Pasteur widened the definition of vaccine in honour of Jenner and it then became essential to qualify the term, by referring to polio vaccine, measles vaccine etc.
OPV also provided longer-lasting immunity than the Salk vaccine, as it provides both humoral immunity and cell-mediated immunity.

Smallpox

small poxsmall-poxvariola
In Europe, the induction of active immunity emerged in an attempt to contain smallpox.
Vaccination immunity declined over time and was probably lost within thirty years.

Cowpox

cowpox virusCow Poxcow-pox
In 1798, Edward Jenner introduced the far safer method of deliberate infection with cowpox virus, (smallpox vaccine), which caused a mild infection that also induced immunity to smallpox.
Once vaccinated, a patient develops antibodies that make them immune to cowpox, but they also develop immunity to the smallpox virus, or Variola virus.

Immunoglobulin A

IgAimmunoglobulin alpha-chainsA
Passive immunity is also provided through the transfer of IgA antibodies found in breast milk that are transferred to the gut of the infant, protecting against bacterial infections, until the newborn can synthesize its antibodies.
Immunoglobulin A (IgA, also referred to as sIgA in its secretory form) is an antibody that plays a crucial role in the immune function of mucous membranes.

Inoculation

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Around the fifteenth century in India, the Ottoman Empire, and east Africa, the practice of inoculation (poking the skin with powdered material derived from smallpox crusts) became quite common.
This generally produced a less severe infection than naturally-acquired smallpox, but still induced immunity to it. This first method for smallpox prevention, smallpox inoculation, is now also known as variolation.

Tetanus

lockjawanti-tetanuslock jaw
In 1888 Emile Roux and Alexandre Yersin isolated diphtheria toxin, and following the 1890 discovery by Behring and Kitasato of antitoxin based immunity to diphtheria and tetanus, the antitoxin became the first major success of modern therapeutic Immunology.
Unlike many infectious diseases, recovery from naturally acquired tetanus does not usually result in immunity to tetanus.

Antibody

antibodiesimmunoglobulinimmunoglobulins
Passive immunity can occur naturally, when maternal antibodies are transferred to the foetus through the placenta, and can also be induced artificially, when high levels of human (or horse) antibodies specific for a pathogen or toxin are transferred to non-immune individuals.
Antibodies contribute to immunity in three ways: They prevent pathogens from entering or damaging cells by binding to them; they stimulate removal of pathogens by macrophages and other cells by coating the pathogen; and they trigger destruction of pathogens by stimulating other immune responses such as the complement pathway.

Immune response

immunological responseimmuneadaptative immune response
Naturally acquired active immunity occurs when a person is exposed to a live pathogen and develops a primary immune response, which leads to immunological memory.
The immune response can include immunity to pathogenic microorganisms and its products, allergies, graft rejections, as well as autoimmunity to self-antigens.

Poliomyelitis

polioinfantile paralysisparalytic polio
Live attenuated polio and some typhoid and cholera vaccines are given orally in order to produce immunity based in the bowel.
Individuals who are exposed to the virus, either through infection or by immunization with polio vaccine, develop immunity.

Yellow fever

yellow fever virusyellow-feveryellow plague
Live, attenuated vaccines are composed of micro-organisms that have been cultivated under conditions which disable their ability to induce disease. These responses are more durable and do not generally require booster shots. Examples include yellow fever, measles, rubella, and mumps.
Surviving the infection provides lifelong immunity, and normally no permanent organ damage results.

Original antigenic sin

Hoskins effect
Original antigenic sin, also known as the Hoskins effect, refers to the propensity of the body's immune system to preferentially utilize immunological memory based on a previous infection when a second slightly different version of that foreign entity (e.g. a virus or bacterium) is encountered.

Premunity

immunity
Premunity
Premunity is a term used to signify progressive development of immunity in individuals exposed to an infective agent, mainly belonging to protozoa and Rickettsia, but not in viruses.

Vaccine-naive

Vaccine-naive
Vaccine-naive is a lack of immunity, or immunologic memory, to a disease because the person has not been vaccinated.

Antivenom

antiveninanti-venomantivenins
Antivenin
However, unlike a vaccination against disease which must only produce a latent immunity that can be roused in case of infection in order to neutralize a sudden and large dose of venom requires maintaining a high level of circulating antibody (a hyperimmunized state), through repeated venom injections (typically every 21 days).

Antibiotic

antibioticsantibacterialantibacterials
The artificial induction of passive immunity has been used for over a century to treat infectious disease, and before the advent of antibiotics, was often the only specific treatment for certain infections.
Vaccines rely on immune modulation or augmentation.

Hepatitis A

hepatitis A virusAinfectious hepatitis
Inactivated vaccines are composed of micro-organisms that have been killed with chemicals and/or heat and are no longer infectious. Examples are vaccines against flu, cholera, plague, and hepatitis A. Most vaccines of this type are likely to require booster shots.
Infection is common in children in developing countries, reaching 100% incidence, but following infection, lifelong immunity results.