- Humoral immunity
The Humoral Immune Response (HIR) is the aspect of immunity that is mediated by secreted
antibodies(as opposed to cell-mediated immunitywhich involves T lymphocytes) produced in the cells of the B lymphocytelineage ( B cell). Secreted antibodies bind to antigens on the surfaces of invading microbes (such as viruses or bacteria), which flags them for destruction.cite book | author = Pier GB, Lyczak JB, Wetzler LM | title = Immunology, Infection, and Immunity | edition = | publisher = ASM Press| year = 2004 | id = ISBN 1-55581-246-5] Humoral immunity is called as such, because it involves substances found in the humours, or body fluids.
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 is divided into a more primitive innate immune system, and acquired or adaptive immune systemof vertebrates, the latter of which is further divided into humoral and cellular components.
Humoral immunity refers to antibody production, and the accessory processes that accompany it, including:
Th2activation and cytokineproduction, germinal centerformation and isotypeswitching, affinity maturationand memory cellgeneration. It also refers to the effector functions of antibody, which include pathogen and toxin neutralization, classical complement activation, and opsoninpromotion of phagocytosisand pathogen elimination.cite book | author = Janeway CA, Jr. "et al" | title = Immunobiology. | edition = 5th ed. | publisher = Garland Publishing | year = 2001 | id = [http://www.ncbi.nlm.nih.gov/books/bv.fcgi?call=bv.View..ShowTOC&rid=imm.TOC&depth=10 (electronic full text via NCBI Bookshelf)] ISBN 0-8153-3642-X ]
The concept of humoral immunity developed based on analysis of
antibacterialactivity of the components of serum. Hans Buchneris credited with the development of the humoral theory.Metchnikoff, Elie (1905) [http://books.google.com/books?vid=OCLC03666307&id=ywKp9YhK5t0C&printsec=titlepage&vq=Ehrlich&dq=history+of+humoral+immunity Immunity in infectious disease] (Full Text Version) Cambridge University Press] In 1890 he described alexins, or “protective substances”, which exist in the serum and other bodily fluids and are capable of killing microorganisms. Alexins, later redefined "complement" by Paul Ehrlich, were shown to be the solublecomponents of the innate response that lead to a combination of cellular and humoral immunity, and bridged the features of innate and acquired immunity.
Following the 1888 discovery of
diphtheriaand tetanus, Emil von Behringand Shibasaburo Kitasatoshowed that disease need not be caused by microorganisms themselves. They discovered that cell-free filtrates were sufficient to cause disease. In 1890, filtrates of diphtheria (later named diphtheria toxins) were used to immunize animals in an attempt to demonstrate that immunized serum contained an antitoxinthat could neutralize the activity of the toxin and could transfer immunity to non immune animals.Gherardi E. [http://nfs.unipv.it/nfs/minf/dispense/immunology/expfound.html The experimental foundations of Immunology] Immunology Course Medical School, University of Pavia.] In 1897, Paul Ehrlich showed that antibodies form against the plant toxins ricinand abrin, and proposed that these antibodies are responsible for immunity. Ehrlich, with his friend Emil von Behring, went on to develop the diphtheria antitoxin, which became the first major success of modern immunotherapy. The presence and specificity of antibodies became the major tool for standardizing the state of immunity and identifying the presence of previous infections.
The complement system is a biochemical cascade of the immune system that helps clear pathogens from an organism. It is derived from many small plasma
proteinsthat work together to disrupt the target cell's plasma membraneleading to cytolysis of the cell. The complement system consists of more than 35 soluble and cell-bound proteins, 12 of which are directly involved in the complement pathways. The complement system is involved in the activities of both innate immunity and acquired immunity.
Activation of this system leads to
cytolysis, chemotaxis, opsonization, immune clearance, and inflammation, as well as the marking of pathogens for phagocytosis. The proteins account for 5% of the serum globulinfraction. Most of these proteins circulate as zymogens, which are inactive until proteolytic cleavage.
Three biochemical pathways activate the complement system: the
classical complement pathway, the alternate complement pathway, and the mannose-binding lectin pathway. The classical complement pathway typically requires antibodies for activation and is a specific immune response, while the alternate pathway can be activated without the presence of antibodies and is considered a non-specific immune response. Antibodies, in particular the IgG1 class, can also "fix" complement.
Immunoglobulins are glycoproteins in the immunoglobulin superfamily that function as antibodies. The terms "antibody" and "immunoglobulin" are often used interchangeably. They are found in the blood and tissue fluids, as well as many secretions. In structure, they are large Y-shaped globular proteins. In mammals there are five types of antibody: IgA, IgD, IgE, IgG, and IgM. Each immunoglobulin class differs in its biological properties and has evolved to deal with different antigens. Antibodies are synthesized and secreted by plasma cells that are derived from the B cells of the immune system.
An antibody is used by the immune system to identify and neutralize foreign objects like bacteria and viruses. Each antibody recognizes a specific antigen unique to its target. By binding their specific antigens, antibodies can cause agglutination and precipitation of antibody-antigen products, prime for phagocytosis by macrophages and other cells, block
viralreceptors, and stimulate other immune responses, such as the complement pathway.
blood transfusion, causes a transfusion reaction, which is mediated by the humoral immune response. This type of reaction, called an acute hemolytic reaction, results in the rapid destruction ( hemolysis) of the donor red blood cells by host antibodies. The cause is usually a clerical error (i.e. the wrong unit of blood being given to the wrong patient). The symptoms are fever and chills, sometimes with back pain and pink or red urine( hemoglobinuria). The major complication is that hemoglobinreleased by the destruction of red blood cells can cause acute renal failure.
The principal function of B cells is to make antibodies against soluble antigens. B cell recognition of antigen is not the only element necessary for B cell activation (a combination of clonal
proliferationand terminal differentiationinto plasma cells).
Naive B cells can be activated in a T-cell dependent or independent manner, but two signals are always required to initiate activation.
B cell activation depends on one of three mechanisms: "Type 1 T cell-independent" (polyclonal) activation, "Type 2 T cell-independent" activation (in which macrophages present several of the same antigen in a way that causes cross-linking of antibodies on the surface of B cells), and, T cell-dependent activation. During
T cell-dependent activation, an antigen presenting cell(APC) presents a processed antigen to a helper T (Th) cell, priming it. When a B cell processes and presents the "same" antigen to the "primed Th cell", the T cell releases cytokines that activate the B cell.
*The following article reviews some of the early experiments that laid the foundations of the humoral theory:Meltzer, S. J. and Charles Norris (1897) [http://www.jem.org/cgi/reprintframed/2/6/701 The Bactericidal Action of Lymph Taken From the Thoracic Duct of the Dog. (Full Text-pdf)] Journal of Experimental Medicine Vol. 2, Issue 6, 701-709.
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Look at other dictionaries:
humoral immunity — Immunol. See antibody mediated immunity. * * * humoral immunity noun An acquired immunity in which antibodies circulating in body fluids play the major part • • • Main Entry: ↑humour … Useful english dictionary
humoral immunity — immunity mediated by antibodies. Cf. cell mediated i … Medical dictionary
humoral immunity — noun Immunity to infection due to antibodies, which circulate in the blood and lymph, and which are produced by B cells. Syn: antibody mediated immunity … Wiktionary
humoral immunity — Immunol. See antibody mediated immunity. * * * … Universalium
Immunity (medical) — Immunity is a biological term that describes a state of having sufficient biological defenses to avoid infection, disease, or other unwanted biological invasion. Immunity involves both specific and non specific components. The non specific… … Wikipedia
Humoral immune deficiency — Humoral immune deficiencies are conditions which cause impairment of humoral immunity, which can lead to immunodeficiency. It can be mediated by failures of B cells, the plasma cells they differentiate into, or the antibody secreted by the plasma … Wikipedia
Humoral — Pertaining to elements in the blood or other body fluids. In medicine, humor refers to a fluid (or semifluid) substance. Thus, the aqueous humor is the fluid normally present in the front and rear chambers of the eye. The humors were part of an… … Medical dictionary
humoral — adj. circulating in the bloodstream; humoral immunity requires circulating antibodies … The new mediacal dictionary
Immunity — The condition of being immune. Immunity can be innate (for example, humans are innately immune to canine distemper) or conferred by a previous infection or immunization. * * * 1. The status or quality of being immune (1). 2. Protection against… … Medical dictionary
humoral — (antibody mediated) immunity (hu mor al) The type of immunity that results from the presence of soluble antibodies in blood and lymph; also known as antibody mediated immunity … Dictionary of microbiology