Immunology

Immunology is a broad branch of biomedicalsciencethat covers the study of all aspects of the immune systemin all organisms. It deals with, among other things, the physiologicalfunctioning of the immune system in states of both health and disease; malfunctions of the immune system in immunological disorders (autoimmune diseases, hypersensitivities, immune deficiency, allograftrejection); the physical, chemical and physiological characteristics of the components of the immune system in vitro, in situ, and in vivo. Immunology has various applications in several disciplines of science, and as such is further divided.

Histological examination of the immune system

Even before the concept of immunity(from immunis, Latin for "exempt") was developed, numerous early physicians characterised organs that would later prove to be part of the immune system. The key organs of the immune system are thymus, spleen, bone marrow, lymph vessels, lymph nodesand secondary lymphatic tissues such as tonsils, adenoids, and skin. Two major organs, the thymus and spleen, are examined histologicallyonly post-mortem during autopsy. However some lymph nodes and secondary lymphatic tissues can be surgicallyexcised for examination while patients are still alive.

Many components of the immune system are actually cellularin nature and not associated with any specific organ but rather are embedded or circulating in various tissueslocated throughout the body.

Classical immunology

Classical immunology ties in with the fields of epidemiologyand medicine. It studies the relationship between the body systems, pathogens, and immunity. The earliest written mention of immunity can be traced back to the plagueof Athensin 430 BCE. Thucydidesnoted that people who had recovered from a previous bout of the disease could nursethe sick without contracting the illness a second time. Many other ancient societies have references to this phenomenon, but it was not until the 19thand 20th centuriesbefore the concept developed into scientific theory.

The study of the molecular and cellular components that comprise the immune system, including their function and interaction, is the central science of immunology. The immune system has been divided into a more primitive innate immune system, and acquired or adaptive immune systemof vertebrates, the latter of which is further divided into humoraland cellular components.

The humoral (antibody) response is defined as the interaction between antibodiesand antigens. Antibodies are specific proteins released from a certain class of immune cells (B lymphocytes). Antigens are defined as anything that elicits generation of antibodies, hence they are Antibody Generators. Immunology itself rests on an understanding of the properties of these two biological entities. However, equally important is the cellular response, which can not only kill infected cells in its own right, but is also crucial in controlling the antibody response. Put simply, both systems are highly interdependent.

In the 21st century, immunology has broadened its horizons with much research being performed in the more specialized niches of immunology. This includes the immunological function of cells, organs and systems not normally associated with the immune system, as well as the function of the immune system outside classical models of immunity.

Clinical immunology

Clinical immunologyis the study of diseasescaused by the immune system and diseases of the immune system from a medical perspective.

Many diseases caused by the immune system fall into two broad categories: immunodeficiency, in which parts of the immune system fail to provide an adequate response (examples include chronic granulomatous disease), and autoimmunity, in which the immune system attacks its own host's body (examples include systemic lupus erythematosus, rheumatoid arthritis, Hashimoto's diseaseand myasthenia gravis). Other immune system disorders include different hypersensitivities, in which the system responds inappropriately to harmless compounds (asthmaand allergies) or responds too intensely.

The most well-known disease that affects the immune system itself is AIDS, caused by the HIV virus. AIDS is an immunodeficiency characterized by the lack of CD4+ ("helper") T cellsand macrophages, which are destroyed by the HIV virus.

Clinical immunologists also study ways to prevent transplant rejection, in which the immune system attempts to destroy allograftsor xenografts.

Immunotherapy

See main article Immunotherapy

The use of immune system components to treat a disease or disorder is known as immunotherapy. Immunotherapy is most commonly used in the context of the treatment of cancerstogether with chemotherapy(drugs) and radiotherapy(radiation). However, immunotherapy is also often used in the immunosuppressed (such as HIVpatients) and people suffering from other immune deficiencies or autoimmune diseases.

Diagnostic immunology

The specificity of the bond between antibody and antigen has made it an excellent tool in the detection of substances in a variety of diagnostic techniques. Antibodies specific for a desired antigencan be conjugated with a radiolabel, fluorescent label, or color-forming enzyme and are used as a "probe" to detect it.

Well known applications of this include immunoblotting, ELISAand immunohistochemical staining of microscope slides. The speed, accuracy and simplicity of such tests has led to the development of rapid techniques for the diagnosis of disease, microbes and even illegal drugs in vivo (of course tests conducted in a closed environment have a higher degree of accuracy). Such testing is also used to distinguish compatible blood types.

Evolutionary immunology

Study of the immune system in extant and extinctspecies is capable of giving us a key understanding of the evolutionof species and the immune system.

A development of complexity of the immune system can be seen from simple phagocytotic protection of single celled organisms, to circulating antimicrobial peptides in insects to lymphoid organs in vertebrates. Of course, like much of evolutionary observation, these physical properties are often seen from the anthropocentricaspect. It should be recognised, that every organism living today has an immune system absolutely capable of protecting it from most forms of harm; those organisms that did not adapt their immune systems to external threats are no longer around to be observed.

Insectsand other arthropods, while not possessing true adaptive immunity, show highly evolved systems of innate immunity, and are additionally protected from external injury (and exposure to pathogens) by their chitinousshells.

See also

• Immune system
• autoimmunity
• List of immunologists

References

• Wikibooks Immunology Textbook
• Goldsby RA, Kindt TK, Osborne BA and Kuby J (2003) Immunology, 5th Edition, W.H. Freeman and Company, New York, New York, ISBN 0-7167-4947-5cs:Imunologie

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It uses material from the http://en.wikipedia.org/wiki/Immunology Wikipedia article Immunology.