The buffy coat is the fraction of an anticoagulated

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 ...

sample that contains most of the white blood cells and

platelet Platelets, also called thrombocytes (from Greek θρόμβος, "clot" and κύτος, "cell"), are a component of blood whose function (along with the coagulation factors) is to react to bleeding from blood vessel injury by clumping, thereby i ...

s following centrifugation. It is rich in a number of

immune cells White blood cells, also called leukocytes or leucocytes, are the cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders. All white blood cells are produced and derived from mult ...

including

leukocytes White blood cells, also called leukocytes or leucocytes, are the cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders. All white blood cells are produced and derived from mult ...

, granulocytes.

Description

After centrifugation, one can distinguish a layer of clear fluid (the plasma), a layer of red fluid containing most of the

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 ...

s, and a thin layer in between. Composing less than 1% of the total volume of the blood sample, the buffy coat (so-called because it is usually

buff Buff or BUFF may refer to: People * Buff (surname), a list of people * Buff (nickname), a list of people * Johnny Buff, ring name of American world champion boxer John Lisky (1888–1955) * Buff Bagwell, a ring name of American professional ...

in hue), contains most of the white blood cells and

s. The buffy coat is usually whitish in color, but is sometimes green if the blood sample contains large amounts of neutrophils, which are high in green-colored

myeloperoxidase Myeloperoxidase (MPO) is a peroxidase enzyme that in humans is encoded by the ''MPO'' gene on chromosome 17. MPO is most abundantly expressed in neutrophil granulocytes (a subtype of white blood cells), and produces hypohalous acids to carry ...

. The layer beneath the buffy coat contains

granulocytes Granulocytes are cells in the innate immune system characterized by the presence of specific granules in their cytoplasm. Such granules distinguish them from the various agranulocytes. All myeloblastic granulocytes are polymorphonuclear. They ha ...

and red blood cells. The buffy coat is commonly used for DNA extraction, with white blood cells providing approximately 10 times more concentrated sources of nucleated cells. They are extracted from the blood of mammals because mammalian red blood cells are anucleate and do not contain DNA. A common protocol is to store buffy coat specimens for future DNA isolation and these may remain in frozen storage for many years. Some refer to the buffy coat when separating cells by

Ficoll Ficoll is a neutral, highly branched, high-mass, hydrophilic polysaccharide which dissolves readily in aqueous solutions. Ficoll radii range from 2-7 nm. It is prepared by reaction of the polysaccharide with epichlorohydrin. Ficoll is a regi ...

density gradients. This usage of the expression buffy coat is incorrect.

Diagnostic uses

Quantitative buffy coat (QBC), based on the centrifugal stratification of blood components, is a

laboratory A laboratory (; ; colloquially lab) is a facility that provides controlled conditions in which scientific or technological research, experiments, and measurement may be performed. Laboratory services are provided in a variety of settings: physic ...

test for the detection of malarial parasites, as well as of other blood

parasite Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...

s. The blood is taken in a QBC capillary tube which is coated with

acridine orange Acridine orange is an organic compound that serves as a nucleic acid-selective fluorescent dye with cationic properties useful for cell cycle determination. Acridine orange is cell-permeable, which allows the dye to interact with DNA by interca ...

(a fluorescent dye) and centrifuged; the fluorescing parasitized erythrocytes get concentrated in a layer which can then be observed by

fluorescence microscopy A fluorescence microscope is an optical microscope that uses fluorescence instead of, or in addition to, scattering, reflection, and attenuation or absorption, to study the properties of organic or inorganic substances. "Fluorescence microscop ...

, under

ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation ...

light at the interface between red blood cells and buffy coat. This test is more sensitive than the conventional

thick smear A blood smear, peripheral blood smear or blood film is a thin layer of blood smeared on a glass microscope slide and then stained in such a way as to allow the various blood cells to be examined microscopically. Blood smears are examined in the ...

and in > 90% of cases the species of parasite can also be identified. In cases of extremely low white blood cell count, it may be difficult to perform a manual differential of the various types of white cells, and it may be virtually impossible to obtain an automated differential. In such cases, the

medical technologist A medical laboratory scientist (MLS) or clinical laboratory scientist (CLS) or medical technologist (MT) performs diagnostic testing of blood and body fluids in clinical laboratories. The scope of a medical laboratory scientist's work begins wit ...

may obtain a buffy coat, from which a blood smear is made. This smear contains a much higher number of white blood cells than whole blood.

References

External links

* {{MeshName, Blood Buffy Coat Blood Immunology Malaria

Description

Diagnostic uses

See also

References

External links