Immune system
The set of tissues which work together to resist infections is called the immune system. The immune mechanisms help an organism identify a pathogen, and neutralize its threat.
The immune system can detect and identify many different kinds of disease agents. Examples are viruses, bacteria and parasites. The immune system can detect a difference between the body's own healthy cells or tissues, and 'foreign' cells. Detecting an unhealthy intruder is complicated, because intruders can evolve and adapt so that the immune system will no longer detect them.
Once a foreign cell or protein is detected, the immune system creates antibodies to fight the intruders, and sends special cells ('phagocytes') to eat them up.
Even simple unicellular organisms such as bacteria possess enzyme systems that protect against viral infections. Other basic immune mechanisms appeared in ancient life forms and remain in their modern descendants, such as plants and insects. These mechanisms include antimicrobial peptides called defensins, phagocytosis, and the complement system. These are the innate immune system, which defends the host from infections in a non-specific way.[1] The simplest innate system is the cell wall or barrier on the outside to stop intruders getting in. For example, skin stops most outside bacteria getting in.
Vertebrates, including humans, have much more sophisticated defense mechanisms. Whereas the innate immune system is found in all metazoa, the adaptive immune system is only found in vertebrates. It is thought to have arisen in the first jawed vertebrates.
The adaptive immune response gives the vertebrate immune system the ability to recognize and remember specific pathogens. The system mounts stronger attacks each time the pathogen is encountered. It is adaptive immunity because the body's immune system prepares itself for future challenges.
The typical vertebrate immune system consists of many types of proteins, cells, organs, and tissues that interact in a complex and ever-changing network. The "acquired immunity" and creates akind of immunological memory.
This process of acquired immunity is the basis of vaccination. Primary response can take 2 days to even 2 weeks to develop. After the body gains immunity towards a certain pathogen, when infection by that pathogen occurs again, the immune response is called the secondary response.
In some organisms, the immune system has its own problems within itself, called disorders. These result in other diseases, including autoimmune diseases, inflammatory diseases and possibly even cancer.[2][3] Immunodeficiency diseases occur when the immune system is less active than normal. Immunodeficiency can either be the result of a genetic (inherited) disease, or an infection, such as the acquired immune deficiency syndrome (AIDS), that is caused by the retrovirus HIV, or other causes.
In contrast, autoimmune diseases result from an immune system that attacks normal tissues as if they were foreign organisms. Common autoimmune diseases include Hashimoto's thyroiditis, rheumatoid arthritis, diabetes mellitus type 1, and lupus erythematosus.
Immunology is the study of all aspects of the immune system. It is very important to health and diseases.
[change] History of immunology
Immunology is a science that examines the structure and function of the immune system. It originates from medicine and early studies on the causes of immunity to disease. The earliest known mention of immunity was during the plague of Athens in 430 BC. Thucydides (460-395 BC) noted that people who had recovered from a previous bout of some diseases could nurse the sick without contracting the illness a second time.[4] In the 18th century, Pierre-Louis Moreau de Maupertuis made experiments with scorpion venom and observed that certain dogs and mice were immune to this venom.[5] This and other observations of acquired immunity was later exploited by Louis Pasteur (1822-1895) in his development of vaccination and his proposed Germ theory of disease.[6] Pasteur's theory was in direct opposition to contemporary theories of disease, such as the miasma theory. It was not until the proofs of Robert Koch (1843-1910) published in 1891, for which he was awarded a Nobel Prize in 1905, that microorganisms were confirmed as the cause of infectious disease.[7] Viruses were confirmed as human pathogens in 1901, with the discovery of the yellow fever virus by Walter Reed (1851-1902).[8]
Immunology made a great advance towards the end of the 19th century, through rapid developments, in the study of humoral immunity and cellular immunity.[9] Particularly important was the work of Paul Ehrlich (1854-1915), 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, Ilya Mechnikov (1845-1916).[10]
[change] References
- ↑ Beck, Gregory; Gail S. Habicht (November 1996). "Immunity and the invertebrates" (PDF). Scientific American: 60–66. http://www.scs.carleton.ca/~soma/biosec/readings/sharkimmu-sciam-Nov1996.pdf. Retrieved 1 January 2007.
- ↑ "Inflammatory Cells and Cancer", Lisa M. Coussens and Zena Werb 2001. Journal of Experimental Medicine, 193 F23-26.
- ↑ "Chronic immune activation and inflammation as the cause of malignancy" K.J. O'Byrne and A.G. Dalgleish 2010. British Journal of Cancer. 85, 473-483.
- ↑ Retief FP, Cilliers L (January 1998). "The epidemic of Athens, 430-426 BC". South African Medical Journal 88 (1): 50–3. PMID 9539938.
- ↑ Ostoya P (1954). "Maupertuis et la biologie". Revue d'histoire des sciences et de leurs applications 7 (1): 60–78. doi:10.3406/rhs.1954.3379. http://www.persee.fr/web/revues/home/prescript/article/rhs_0048-7996_1954_num_7_1_3379.
- ↑ Plotkin SA (April 2005). "Vaccines: past, present and future". Nature Medicine 11 (4 Suppl): S5–11. doi:10.1038/nm1209. PMID 15812490.
- ↑ The Nobel Prize in Physiology or Medicine 1905, Nobelprize.org, accessed 8 January 2007.
- ↑ Major Walter Reed, U.S. Army, Walter Reed Army Medical Center, accessed 8 January 2007.
- ↑ Mechnikov, Ilya; Translated by F.G. Binnie (1905) (Full Text Version: Google Books). Immunity in Infective Diseases. Cambridge University Press. ISBN 68025143. http://books.google.com/?id=ywKp9YhK5t0C&printsec=titlepage&vq=Ehrlich&dq=history+of+humoral+immunity.
- ↑ The Nobel Prize in Physiology or Medicine 1908, Nobelprize.org, accessed 8 January 2007.
