Agglutination is the clumping of particles. The word ''agglutination'' comes from the

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

'' agglutinare'' (glueing to). Agglutination is a reaction in which particles (as red blood cells or bacteria) suspended in a liquid collect into clumps usually as a response to a specific antibody. Agglutinatie_rode_bloedcellen_libtheora

This occurs in biology in two main examples: # The clumping of cells such as bacteria or red blood cells in the presence of an

antibody An antibody (Ab) or immunoglobulin (Ig) is a large, Y-shaped protein belonging to the immunoglobulin superfamily which is used by the immune system to identify and neutralize antigens such as pathogenic bacteria, bacteria and viruses, includin ...

complement Complement may refer to: The arts * Complement (music), an interval that, when added to another, spans an octave ** Aggregate complementation, the separation of pitch-class collections into complementary sets * Complementary color, in the visu ...

. The antibody or other molecule binds multiple particles and joins them, creating a large complex. This increases the efficacy of microbial elimination by

phagocytosis Phagocytosis () is the process by which a cell (biology), cell uses its plasma membrane to engulf a large particle (≥ 0.5 μm), giving rise to an internal compartment called the phagosome. It is one type of endocytosis. A cell that performs ph ...

as large clumps of bacteria can be eliminated in one pass, versus the elimination of single microbial antigens. # When people are given blood transfusions of the wrong blood group, the antibodies react with the incorrectly transfused blood group and as a result, the

erythrocytes Red blood cells (RBCs), referred to as erythrocytes (, with -''cyte'' translated as 'cell' in modern usage) in academia and medical publishing, also known as red cells, erythroid cells, and rarely haematids, are the most common type of blood cel ...

clump up and stick together causing them to agglutinate. The coalescing of small particles that are suspended in a solution; these larger masses are then (usually) precipitated.

In immunohematology

Hemagglutination

Hemagglutination Hemagglutination, or haemagglutination, is a specific form of agglutination that involves red blood cells (RBCs). It has two common uses in the laboratory: blood typing and the quantification of virus dilutions in a haemagglutination assay. Blo ...

is the process by which

red blood cell Red blood cells (RBCs), referred to as erythrocytes (, with -''cyte'' translated as 'cell' in modern usage) in academia and medical publishing, also known as red cells, erythroid cells, and rarely haematids, are the most common type of blood cel ...

s agglutinate, meaning clump or clog. The agglutin involved in hemagglutination is called

hemagglutinin The term hemagglutinin (alternatively spelt ''haemagglutinin'', from the Greek , 'blood' + Latin , 'glue') refers to any protein that can cause red blood cells (erythrocytes) to clump together (" agglutinate") ''in vitro''. They do this by bindin ...

. In

cross-matching Cross-matching or crossmatching is a test performed before a blood transfusion as part of blood compatibility testing. Normally, this involves adding the recipient's blood plasma to a sample of the donor's red blood cells. If the blood is incom ...

donor A donor in general is a person, organization or government which donates something voluntarily. The term is usually used to represent a form of pure altruism, but is sometimes used when the payment for a service is recognized by all parties as re ...

red blood cells and the recipient's serum or plasma are incubated together. If agglutination occurs, this indicates that the donor and recipient blood types are incompatible. When a person produces

antibodies An antibody (Ab) or immunoglobulin (Ig) is a large, Y-shaped protein belonging to the immunoglobulin superfamily which is used by the immune system to identify and neutralize antigens such as bacteria and viruses, including those that caus ...

against their own red blood cells, as in

cold agglutinin disease Cold agglutinin disease (CAD) is a 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 , directed again ...

and other

autoimmune In immunology, autoimmunity is the system of immune responses of an organism against its own healthy cells, tissues and other normal body constituents. Any disease resulting from this type of immune response is termed an " autoimmune disease" ...

conditions, the cells may agglutinate spontaneously. This is called

autoagglutination In hematology, red cell agglutination or autoagglutination is a phenomenon in which red blood cells clump together, forming aggregates. It is caused by the surface of the red cells being coated with antibodies. This often occurs in cold agglutini ...

and it can interfere with laboratory tests such as

blood typing Blood compatibility testing is conducted in a medical laboratory to identify potential incompatibilities between Human blood group systems, blood group systems in blood transfusion. It is also used to diagnose and prevent some complications of pr ...

and the

complete blood count A complete blood count (CBC), also known as a full blood count (FBC) or full haemogram (FHG), is a set of medical laboratory tests that provide cytometry, information about the cells in a person's blood. The CBC indicates the counts of white blo ...

Leukoagglutination

Leukoagglutination occurs when the particles involved are

white blood cell White blood cells (scientific name leukocytes), also called immune cells or immunocytes, are cells of the immune system that are involved in protecting the body against both infectious disease and foreign entities. White blood cells are genera ...

s. An example is the PH-L form of

phytohaemagglutinin Phytohaemagglutinin (PHA, or phytohemagglutinin) is a lectin found in plants, especially certain legumes. PHA actually consists of two closely related proteins, called leucoagglutinin (PHA-L) and PHA-E. These proteins cause blood cells to clump ...

In microbiology

Agglutination is commonly used as a method of identifying specific bacterial antigens and the identity of such bacteria, and therefore is an important technique in diagnosis.

History of discoveries

Two bacteriologists, Herbert Edward Durham (1866-1945) and

Max von Gruber Max von Gruber (6 July 1853, in Vienna – 16 September 1927, in Berchtesgaden) was an Austrian scientist and Eugenics, eugenicist. As a bacteriologist he discovered specific Agglutination (biology), agglutination in 1896 with his English colleag ...

(1853–1927), discovered specific agglutination in 1896. The clumping became known as Gruber-Durham reaction. Gruber introduced the term agglutinin (from the Latin) for any substance that caused agglutination of cells. French physician

Fernand Widal Georges-Fernand-Isidor Widal (March 9, 1862 in Dellys, Algeria – January 14, 1929 in Paris) was a French physician. From 1886 to 1888 he devoted himself to public demonstrations of the researches of the faculty of pathological anatomy, and duri ...

(1862–1929) put Gruber and Durham's discovery to practical use later in 1896, using the reaction as the basis for a test for

typhoid fever Typhoid fever, also known simply as typhoid, is a disease caused by '' Salmonella enterica'' serotype Typhi bacteria, also called ''Salmonella'' Typhi. Symptoms vary from mild to severe, and usually begin six to 30 days after exposure. Often th ...

. Widal found that blood serum from a typhoid carrier caused a culture of typhoid bacteria to clump, whereas serum from a typhoid-free person did not. This

Widal test The Widal test, developed in 1896 and named after its inventor, Georges-Fernand Widal, is an indirect agglutination test for enteric fever or undulant fever whereby bacteria causing typhoid fever are mixed with a serum containing specific anti ...

was the first example of serum diagnosis. Austrian physician

Karl Landsteiner Karl Landsteiner (; 14 June 1868 – 26 June 1943) was an Austrian-American biologist, physician, and immunologist. He emigrated with his family to New York in 1923 at the age of 55 for professional opportunities, working for the Rockefeller ...

found another important practical application of the agglutination reaction in 1900. Landsteiner's agglutination tests and his discovery of ABO blood groups was the start of the science of

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

and

serology Serology is the scientific study of Serum (blood), serum and other body fluids. In practice, the term usually refers to the medical diagnosis, diagnostic identification of Antibody, antibodies in the serum. Such antibodies are typically formed in r ...

which has made transfusion possible and safer.

References