The buffy coat is the

fraction A fraction (from , "broken") represents a part of a whole or, more generally, any number of equal parts. When spoken in everyday English, a fraction describes how many parts of a certain size there are, for example, one-half, eight-fifths, thre ...

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 is com ...

sample that contains most of the

leukocytes 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 ...

and

thrombocytes Platelets or thrombocytes () are a part of blood whose function (along with the coagulation factors) is to react to bleeding from blood vessel injury by clumping to form a blood clot. Platelets have no cell nucleus; they are fragments of cyt ...

following

centrifugation Centrifugation is a mechanical process which involves the use of the centrifugal force to separate particles from a solution according to their size, shape, density, medium viscosity and rotor speed. The denser components of the mixture migrate ...

Description

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

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 ...

, 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 in hue), contains most of the

and

. The buffy coat is usually whitish in color, but is sometimes green if the blood sample contains large amounts of

neutrophils Neutrophils are a type of phagocytic white blood cell and part of innate immunity. More specifically, they form the most abundant type of granulocytes and make up 40% to 70% of all white blood cells in humans. Their functions vary in different ...

, 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 neutrophils (a subtype of white blood cells), and produces hypohalous acids to carry out their anti ...

The buffy coat is commonly used for

DNA Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of al ...

extraction, with leukocytes providing approximately 10 times more concentrated sources of nucleated cells. Mammalian erythrocytes are anucleate and do not contain DNA, so erethrocytes are normally removed for DNA analysis. A common protocol is to store buffy coat specimens for future DNA isolation and these may remain in frozen storage for many years.

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. Laboratories are found in a variety of settings such as schools ...

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

parasite Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted str ...

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 it to interact with DNA by intercalation ...

(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. A fluorescence micro ...

, under

ultraviolet radiation Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of t ...

at the interface between erythrocytes and buffy coat. This test is more sensitive than the conventional thick smear and in over 90% of cases the species of parasite can also be identified. In cases of extremely low leukocyte count, it may be difficult to perform a manual differential of their various types and it may be virtually impossible to obtain an automated differential. In such cases, the medical technologist may obtain a buffy coat, from which a blood smear is made. This smear contains a much higher number of leukocytes than whole blood.

Medical Research

Since the buffy coat is mostly composed of leukocytes, it is a useful in human medical research, especially in cases where blood is the only experimental sample. Peripheral blood mononuclear cells (PBMCs) can be extracted from the buffy coat, and can be frozen for storage, or used to conduct immunological experiments.

References

External links

* {{MeshName, Blood Buffy Coat Blood Immunology Malaria

Description

Diagnostic uses

Medical Research

See also

References

External links