What Really is a Buffy Coat?

The definition of a buffy coat often depends on who you ask.  Buffy coat from a research lab processing point of view is a different product than buffy coat produced from a blood bank or donor center.

Often, the terms buffy coat and PBMCs (peripheral blood mononuclear cells) are used interchangeably, but there are differences between the two in cell subset composition.  Buffy coat commonly refers to the entire white blood cell layer after centrifugation while PBMCs refers to the isolated mononuclear fraction of white blood cells.

When peripheral whole blood is centrifuged, a white blood cell “buffy coat” layer is separated out.  The buffy coat layer contains lymphocytes, monocytes, and granulocytes (Figure 1).  However, when whole blood is layered on a density gradient and centrifuged, a clean PBMC layer is separated out. The PBMC layer contains primarily lymphocytes and monocytes, with very little granulocyte contamination due to differences in density (Figure 2).


In a blood bank or donor center setting, a buffy coat is processed from a whole unit of blood.  After donation, a whole unit of blood is centrifuged in the original collection bag.  Next, the centrifuged unit is placed on an expressor in which the plasma, buffy coat, and RBC (red blood cell) components are transferred into separate bags in a closed, sterile system (Figure 3).

Buffy coat bags contain approximately 75-100mL and have the appearance of whole blood since a small amount of RBCs is expressed into the buffy coat bag.  The buffy coat in the bag contains a mixture of lymphocytes, monocytes, and some granulocytes.

Understanding the end application is important in choosing whether a buffy coat or isolated PBMC product is the appropriate material.  More often than not, researchers require isolated PBMCs, as opposed to buffy coats, since they are highly pure in mononuclear cells: lymphocytes and monocytes.  BioIVT provides isolated PBMCs that have been QC tested for both viability and purity, ensuring high-quality cells to fast-track research.

Being both a provider of buffy coats isolated from whole blood units as well as a provider of isolated peripheral blood mononuclear cells (PBMCs), BioIVT serves customers by offering a variety of different blood-derived immune cell products.

Click here to learn more about BioIVT’s buffy coat products.