Buffy coat

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 leukocytes and thrombocytes.

[2][3] 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.The buffy coat is commonly used for DNA extraction,[4] with leukocytes providing approximately 10 times more concentrated sources of nucleated cells.

A common protocol is to store buffy coat specimens for future DNA isolation and these may remain in frozen storage for many years.

[10] 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 exepriments.

Layer of thrombocytes and leukocytes ("buffy coat") between erythrocytes and blood plasma after gentle centrifugation of whole blood with sodium ethylenediaminetetraacetate anticoagulant.
Human blood after separation by centrifugation. Plasma (upper layer), buffy coat (middle, white-colored layer) and erythrocyte (red blood cell) layer (bottom) can be seen.