Blood that is collected unfiltered from a donor's vein in a designated container is called whole blood. Depending on body size, the blood volume of an adult is around 4-6 liters.
Blood consists of approx. 55-60 % plasma and 40-45 % cellular components. The plasma is mainly composed of water (approx. 90 %), proteins (such as albumin, coagulation factors and immunoglobulins) as well as electrolytes, nutrients and metabolic waste products. The cellular components include erythrocytes (red blood cells), leukocytes (white blood cells) and thrombocytes (platelets).
The blood transports oxygen and carbon dioxide, nutrients, waste products, heat and various active substances (e.g. the body's own cytokines and ingested pharmaceuticals) through the body via an extensive network of arterial and venous vessels.
The formation of blood cells (hematopoiesis) takes place in the bone marrow from multipotent hematopoietic stem cells (HSCs). These differentiate into various precursor cells, which mature into the three main groups: erythropoiesis (formation of erythrocytes), leukopoiesis (formation of leukocytes) and thrombopoiesis (formation of thrombocytes).
Whole blood and cell separation
In order to identify specific cells or cell populations, such as PBMC. In order to be able to isolate blood directly from whole blood, it is essential to mix the blood sample with anticoagulants. Without anticoagulants (especially plasmatic anticoagulants), the blood would clot and a clean separation of the cell components would not be possible. Depending on the analysis, different anticoagulants are used to preserve the cell morphology, coagulability or chemical composition of the blood.
Whole blood and anticoagulation
Anticoagulation describes the inhibition of blood clotting through the administration or addition of anticoagulant substances. In connection with the collection of whole blood, this means that the blood is stabilized during or immediately after collection by mixing it with anticoagulants. This prevents coagulation and makes the blood stable for further processing. The most important anticoagulants can be divided into three main groups:
1. plasma anticoagulants for blood samples and transfusions
2. direct and indirect inhibitors of blood coagulation (systemic anticoagulants)
3. platelet aggregation inhibitors (indirect anticoagulants)
Whole blood and plasma anticoagulants
Plasmatic anticoagulants are mainly used for blood sampling and blood conservation. They prevent the coagulation of blood outside the body (in vitro) by binding or inactivating coagulation factors or calcium (essential for blood coagulation).
The most important plasmatic anticoagulants are EDTA (ethylene-diamine-tetraacetic acid) citrate (e.g. sodium citrate) and heparin.