Derived from the German word "to glue." The process by which cells are made to adhere to one another, usually through the actions of an agglutinin, such as an antibody or a lectin. Certain viruses and bacteria also are capable of agglutinating blood cells. Many agglutinins, particularly the food lectins, are blood type specific. Certain foods clump only the cells of one blood type, but do not react with the cells of another type.
Agglutination is the clumping of particles. This is usually due to an antibody or other molecule binding with multiple particles, and joining them. Agglutination is commonly used as a method of identifying specific bacterial antigens, and in turn, the identity of such bacteria.
It is also the coalescing of small particles that are suspended in solution; these larger masses are then (usually) precipitated.
Agglutination can also be called an allergic reaction type occurrence where cells become more compacted together to prevent foreign materials entering them. This is usually the result of an antigen in the vicinity of the cells.
Agglutination refers to the clumping of cells, such as bacteria or red blood cells, in the presence of an antibody. Because the clumping reaction occurs quickly and is easy to produce, agglutination is an important technique in diagnosis. Agglutination of red blood cells is used in the Coombs test.
Two bacteriologists, Herbert Edward Durham (-1945) and Max von Gruber (1853-1927), discovered specific agglutination in 1896. The clumping became known as Gruber-Durham reaction. Gruber introduced the term agglutinin for any substance that caused agglutination of cells. (The word comes from the Latin agglutinare, "to glue to.")
French physician Fernand Widal (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. 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 was the first example of serum diagnosis.
Austrian physician Karl Landsteiner found another important practical application of the agglutination reaction in 1900. He was able to categorize human blood into four types, based on the clumping reaction of each type to blood serum. Landsteiner's agglutination tests made blood transfusion possible, since physicians could now avoid giving donor blood that would cause the recipient's blood to clump.
Hemagglutination is a more specific form of agglutination that involves red blood cells. Using antibodies that bind to the A or B blood group on a sample of blood, one can determine the blood type of the individual being tested.
Leukoagglutination is when the particles involved are white blood cells.
|Strength Scale||Grade||Value|| Appearance of reaction|
|4+||Complete ||12||A single agglutinate. No free cells detected.|
|3 1/2+||4+w or 3+s||11|
|3+||3+||10||Strong reaction. A number of large agglutinates.|
|2-1/2+||3+w or 2+s||9|
|2+||2+||8||Large agglutinates in a sea of smaller clumps, no free cells. |
|1-1/2||1+s||6||Many medium and small agglutinates and a background of free cells|
|1+||1+||5||Many small agglutinates and a background of free cells|
|1+w||1+w||4||Many very small agglutinates; with many free cells|
|�+ or -||+/ macro||3||Weak granularity in cell suspension. A few macroscopic agglutinatesbut numerous agglutinates microscopically|
|Trace or micro||(+) macro||2||Appears negative macroscopically. A few agglutinates of 6-8 cells inmost fields|
|Questionable or micro||0||1||Rare agglutinates observed microscopically|
|0||0||0||An even cell suspension. No agglutinates observed microscopically.|
INTERPRETATION OF AGGLUTINATION REACTIONS. S-STRONG, W-WEAK. (SOURCE: AABB TECHNICAL MANUAL, 10TH EDITION. AMERICAN ASSOCIATION OF BLOOD BANKS, 1117 NORTH 19TH ST. STE 600 ARLINGTON VA, 22209)