Immunity (medical)

Immunity is the ability of the body to defend itself from 'foreign bodies'. This means rejecting infections, clearing up dust which gets in the lungs, and killing cancer cells. 

Immunity is of two types. Innate immunity protects the host against infection, but has no 'memory', and so gives no long-term immunity.

The second type is adaptive immunity, which does have a kind of 'memory'. It does give long-term protection against specific pathogens.

All animals, plants and fungi have some innate immunity. Vertebrates also have adaptive immunity.

People can be immunised from some diseases by having a vaccination 
(injection of some dead or weakened virus, or bacteria that causes the disease). Vaccination builds on the natural immune system to make a person resist certain diseases. By doing so, the body reacts more quickly to fight the virus/bacteria when it comes. 

History of immunology
Immunology is a science that examines the structure and function of the immune system. The earliest known mention of immunity was during the plague of Athens in 430 BC. Thucydides noted that people who had recovered from a previous bout of the disease could nurse the sick without contracting the illness a second time.

In the 18th century, Pierre-Louis de Maupertuis made experiments with scorpion venom and observed that certain dogs and mice were immune to this venom.

This and other observations of acquired immunity was later exploited by Louis Pasteur in his development of vaccination and his proposed germ theory of disease. Pasteur's theory was in direct opposition to contemporary theories of disease, such as the miasma theory.

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.The Nobel Prize in Physiology or Medicine 1905 Nobelprize.org Accessed 8 January 2007. Viruses were confirmed as human pathogens in 1901, with the discovery of the yellow fever virus by Walter Reed.Major Walter Reed, Medical Corps, U.S. Army Walter Reed Army Medical Center. Accessed 8 January 2007.

Immunology made a great advance towards the end of the 19th century.  Humoral immunity (antibodies) and cellular immunity (T cells and dendritic cells). were all recognised.

Particularly important was the work of Paul Ehrlich, who proposed the side-chain theory to explain the specificity of the antigen-antibody reaction; his contributions to the understanding of humoral immunity were recognized by the award of a Nobel Prize in 1908, which was jointly awarded to the founder of cellular immunology, Elie Mechnikov.The Nobel Prize in Physiology or Medicine 1908 Nobelprize.org Accessed 8 January 2007

 Humoral immunity 
Humoral immunity is immunity that is done by macromolecules. Antibodies, complement proteins, and certain antimicrobial peptides are in extracellular fluids.

 Cell-mediated immunity  
This is an immune response which does not involve antibodies. Cell-mediated immunity is the activation of phagocytes, antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen.

 References 

Category:Immunology