An agglutinin is a substance in the

blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the cir ...

that causes particles to

coagulate Coagulation, also known as clotting, is the process by which blood changes from a liquid to a gel, forming a blood clot. It potentially results in hemostasis, the cessation of blood loss from a damaged vessel, followed by repair. The mechanism o ...

and aggregate; that is, to change from fluid-like state to a thickened-mass (solid) state. Agglutinins can be antibodies that cause antigens to aggregate by binding to the antigen-binding sites of antibodies. Agglutinins can also be any substance other than antibodies, such as sugar-binding protein

lectins Lectins are carbohydrate-binding proteins that are highly specific for sugar groups that are part of other molecules, so cause agglutination of particular cells or precipitation of glycoconjugates and polysaccharides. Lectins have a role in rec ...

. When an agglutinin is added to a uniform suspension of particles, such as bacteria or blood, in a test tube (

in vitro ''In vitro'' (meaning in glass, or ''in the glass'') studies are performed with microorganisms, cells, or biological molecules outside their normal biological context. Colloquially called " test-tube experiments", these studies in biology ...

), agglutinin binds to the agglutinin-specific structure on the particle causing the particles to aggregate and fall to the bottom, leaving a clear suspension. This phenomenon known as

agglutination In linguistics, agglutination is a morphological process in which words are formed by stringing together morphemes, each of which corresponds to a single syntactic feature. Languages that use agglutination widely are called agglutinative lang ...

is of great importance in medicine, as it serves as a diagnostic tool.antu

Medical relevance

Reaction of particles with agglutinin is used to indicate present or past host contact with a pathogen. A host infected with a pathogen produces antibodies to neutralize the pathogen. As a result, the blood of a host applied to a diagnostic kit causes the aggregation of the pathogenic particles due to the antigen-agglutinin interaction. Conversely, agglutination can also be used to identify new bacteria or cells with a specific antigen by exposing them to serum containing known agglutinins. Agglutination, using blood agglutinins known as hemagglutinins, is used diagnostically to identify blood types of human beings based on the reaction between the

erythrocyte Red blood cells (RBCs), also referred to as red cells, red blood corpuscles (in humans or other animals not having nucleus in red blood cells), haematids, erythroid cells or erythrocytes (from Greek ''erythros'' for "red" and ''kytos'' for "holl ...

(

Red blood cell Red blood cells (RBCs), also referred to as red cells, red blood corpuscles (in humans or other animals not having nucleus in red blood cells), haematids, erythroid cells or erythrocytes (from Greek ''erythros'' for "red" and ''kytos'' for "holl ...

) antigens and agglutinins. Human erythrocytes have two main

types Type may refer to: Science and technology Computing * Typing, producing text via a keyboard, typewriter, etc. * Data type In computer science and computer programming, a data type (or simply type) is a set of possible values and a set of allo ...

of antigens (Antigen A and B) expressed in different combinations to give either erythrocytes that express only antigen A, antigen B, antigen A and B together or no antigen at all. When erythrocytes are exposed to hemagglutinins (anti-A and Anti-B antibodies), those expressing antigen A or B coagulate upon contacting anti-A and anti-B hemagglutinins respectively. Erythrocytes expressing both antigens coagulate upon contacting either anti-A or anti-B hemagglutinins while those not expressing any antigen do not coagulate upon contact with any hemagglutinin. This technique serves as a quick and effective method for identifying the blood type of a person and it is essential when

blood transfusion Blood transfusion is the process of transferring blood products into a person's circulation intravenously. Transfusions are used for various medical conditions to replace lost components of the blood. Early transfusions used whole blood, but mo ...

has to be performed quickly to replenish lost blood.

Diseases

Agglutinin might also be associated with diseases of which the most common is an autoimmune disease known as

cold agglutinin disease Cold agglutinin disease (CAD) is a rare disease, rare autoimmune disease characterized by the presence of high concentrations of circulating cold sensitive antibodies, usually IgM and autoantibodies that are also active at temperatures below , dir ...

. In cold agglutinin disease, the body produces agglutinins or antibodies that coagulate erythrocytes and lyse them at room temperature or lower. Under normal circumstances, the lifespan of erythrocytes is 120 days after which they are degraded by the spleen. In individuals that have cold agglutinin disease, the lifespan of erythrocytes is shortened. The rate of erythrocyte production by the bone marrow is lower than the rate of destruction, thus, individuals with cold agglutinin disease develop a form of anemia. A body might produce agglutinins to attack the erythrocytes due to allergies to foods, inhalants, chemicals and infections. A person suffering from this condition will likely have cooler body parts such as fingers, nose, and ears attacked more often than warmer areas such as armpits.

References

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Medical relevance

Diseases

References

See also