Peripheral blood refers to the blood that flows through the extremities as opposed to the inner core of the body and it is this blood that is removed during routine blood donation. In order to obtain peripheral blood mononuclear cells (also known as PBMC), whole blood is drawn and then treated with anticoagulant, placed in a centrifuge and finally is spun down to separate the blood into its individual components of plasma, platelets, red blood cells, leukocytes and lymphocytes.
Another method of separating blood is through apheresis. During this procedure, blood is drawn from a donor in the same way as a routine blood donation, however instead of being collected in a bag, the blood travels via tubing to a machine where the components are separated. The machine will separate the components using either the centrifuge process where the inside of the machine spins like a centrifuge or by filtration using a series of micro filters to separate components by size. After the desired components are collected the blood travels back through the tubing and is reinfused into the donor. Apheresis may be used on patients who exhibit severe symptoms of a disease and removing the constituent helps the symptoms. However this process must be done fairly frequently and is usually used as a last resort, after other methods to control the symptoms have failed.
Leukocytes, also known as white blood cells, contain two sub-types of cells; mononuclear and polymorphonuclear. Mononuclear cells are defined as any cell with a single round nucleus such as monocytes and lymphocytes. Polymorphonuclear cells are cells with a segmented or lobed nucleus such as basophils, eosinphils and neutrophils.
Lymphocytes are the second most prevalent type of white blood cell. They can be large or small but all have a round dark blue nucleus and originate in lymph tissue instead of bone marrow. Lymphocytes main function is the production of cytokines and antibodies; the essential parts of the immune system. Lymphocytes fight infection and disease and also help defend the body against tumors and other abnormalities.
Monocytes are the biggest of all the white blood cells. They originate in bone marrow and their nucleus is irregularly shaped and may appear folded. They mature into macrophages and dendritic cells. When infection or inflammation is present, monocytes move quickly to the area and as macrophages, they devour the foreign bodies. As dendritic cells they also work to trigger the immune response from the lymphocytes.