Peripheral Blood Mononuclear Cell (PBMC)
A peripheral blood mononucleated cell (PBMC) is any WBC having a single round nucleus. Typically lymphocytes, monocytes and macrophages are grouped under this classification. These WBCs are a critical component in the immune system to tackle against infection and adapt to pathogenic intruders. The lymphocyte population consists of T cells (CD4 and CD8 positive ~75%), B cells and NK cells (~25% combined).
These cells can be extracted from whole blood using ficoll, a hydrophilic polysaccharide that separates layers of blood, which will separate the blood into a top layer of plasma, followed by a layer of PBMCs and a bottom fraction of polymorphonuclear cells (such as neutrophils, basophils and eosinophils) and erythrocytes. The polymorphonuclear cells can be further isolated by lysing the red blood cells.
The buffy coat/layer is the fraction of an anti-coagulated blood sample that contains most of the Peripheral Mononuclear Blood cells (Lymphocytes and Monocytes) and platelets following density gradient centrifugation of the blood.
After centrifugation, one can distinguish a layer of clear fluid (the plasma), a layer of red fluid containing most of the red blood cells, and a thin layer in between. Making up 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 white blood cells and platelets. The buffy coat is used mostly for research purposes, to extract DNA from the blood of. The RBCs are discarded most of the time as they have limited diagnostic or research value since they do not have nucleus that contain genetic material.