Apheresis - a very efficient procedure to remove only a certain type of cell from the donor - the rest is returned to the body. In a multicomponent donation, for example, platelets and plasma are taken. This is less stressful for the donor than a whole blood donation, but the procedure is expensive.
A distinction is made between donor apheresis or collection apheresis and therapeutic apheresis.
In the former, cells or plasma are collected; in the latter, cells or plasma are removed.

Blood - fulfils several tasks that can be more or less summarised under the terms "transport & supply". It is a suspension of blood cells - erythrocytes, platelets and leucocytes - in blood plasma. The blood plasma consists of water, proteins, glucose, clotting factors, messenger substances and metabolic waste products. Blood cells are generated in the bone marrow.

Bloodbank - here, the donated blood is first processed (plasma and platelets are separated from the erythrocytes and leukocytes are removed), and subsequently, erythrocyte concentrates, FFP (fresh frozen plasma) and platelet concentrates are produced. The blood bank supplies blood depots of other hospitals with blood products. A blood bank can also have a blood depot itself.
Blood depot - Most hospitals, especially those with surgical or oncology departments, have an intermediate storage facility to shorten the time between a request for blood and its delivery to the patient. 

Blood donation - in most countries, it is a voluntary and non-remunerated donation of 500 ml of blood, further processed into several blood products. Blood products are considered to be drugs.

Blood donors - women and men between 18 and 70 (the upper age is not precisely defined and is decided individually depending on the health and physical condition of the potential donor) who donate blood voluntarily and free of charge. In some countries, you can donate blood at the age of 16.

Buffy coat - if you centrifuge a tube with anticoagulated blood, the same layers always form, which can be easily distinguished from each other and also separated:
  • at the bottom are the erythrocytes
  • on top of the erythrocytes is a very narrow layer of leucocytes
  • on top is the plasma
where the platelets are located depends on the speed at which the tube was centrifuged:
  • if centrifuged very fast, the platelets will collect just above the white cells in the centre of the tube
  • if centrifugation is slow, the platelets remain in the plasma - this is called PRP (Platelet Rich Plasma) or, in the first case PPP (Platelet Poor Plasma)
The layer in the middle of the tube that either consists almost exclusively of leucocytes or contains the platelets is now called the buffy coat.
CCI (Correctet Count Increment) - (platelet increase per ul) x (body surface area in m2)/number of platelets transfused (x 10^11).
Measured after one hour - the value should be at least 7500 or more; after 24 hours, this value should be at least 4000. It is called a refractory state if it is not reached with two consecutive platelet transfusions. In most cases, this is caused by antibodies against HLA antigens on the platelets.
Complement - a group of plasma proteins, mostly with enzyme function, is considered part of the immune system and can be activated in cascade on the surface of cells when required. 
They have two main functions: 
  • to attack and destroy cells directly by forming a water-permeable opening in the cell membrane, causing the cell to burst due to the osmotically inflowing water
  • through their activation, some of the complement factors become decoys for further immune cells and binding sites for antibodies and, in this way, are involved in the immune response

Cytokines - Messenger substances that are produced by different cells and thereby either activate or attract other cells

Erythrocytes - red blood cells, whose primary function is to transport oxygen. The cells have no nucleus and contain haemoglobin to which the O2 is bound. 
Normal values:  
Men 4.3-5.6 x 10^6/µl
Women 4.0-5.4 x 10^6/µl

FFP - fresh frozen plasma - after fractionation of whole blood into erythrocytes, thrombocytes and plasma, the plasma obtained is either frozen for direct transfusion as single donor plasma within 24h or sold to the pharmaceutical companies.

Genotype - defines which gene is detectable in an individual by molecular biology. An example of this would be the Rhesus D gene (RHD). A gene can occur in different variants - different alleles. The gene for the Duffy blood group can appear as either FYA or FYB. The genotype can almost always be used to predict the phenotype - but sometimes, the expression of a gene product is suppressed. There can be several causes for this: Single point mutations of the gene itself, null alleles, and mutations in the start sequence of a gene that result in the genetic information not being transcribed into the RNA and, thus, not being expressed.

See also phenotype.

Haemoglobin - the main component of erythrocytes. Transports oxygen to the organs and removes carbon dioxide. The uptake of O2 and the release of CO2 takes place in the lungs.

Haemolysis - destruction of the red blood cells and release of free haemoglobin. A distinction is made between immunological and non-immunological haemolysis. The first is caused by antibodies (auto or allo) and can occur relatively fast intravascularly due to complement activation. This would include ABO incompatibility. If the antibodies bind to the red cells but do not activate complement, they are intercepted and cleared by reticular cells in the spleen or liver. Non-immunological haemolysis is practically always intravascular and can have many causes: Drugs, toxic substances, mechanical heart valves, etc. Haemolysis during a transfusion can be caused by improper warming of the blood unit or by simultaneous transfusion of the erythrocytes via the same catheter with substances that directly lyse the erythrocytes (e.g., highly concentrated glucose).

HLA - Human Leukocyte Antigens - Genes that encode the Major Histocompatibility Complex. These are proteins that are expressed on all human cells and define our immunological identity.

Leukocytes - white blood cells are part of the immune system. A distinction is made between different groups, all of which have their functions. The lymphocytes can be further subdivided into T and B cells. The T cells are highly differentiated and play a key role in the cellular immune response. The B cells become plasma cells and produce antibodies, thus part of the humoral immune response. And in addition, there are monocytes, macrophages and granulocytes.
Average values depend on age. Newborns may have up to 30,000/µl of leukocytes. In adults, the numbers range between 4,000 and 11,000/µl.

Leukocytes depletion - for over 20 years, white blood cells have been removed from all blood products in Austria by filtration during manufacturing (the maximum permissible cell content of leukocytes is 10^6 cells).

Octaplas - the most common plasma product in Austria. FFP from several hundred donors is pooled, pathogen-inactivated by various procedures and returned to the blood banks as Octaplas.

Phenotype - is, in its simplest form, the appearance of a gene product. If the RHD gene is expressed, the phenotype of the individual will be Rhesus D positive. Taking the Duffy blood group as an example, the gene may be present in the FYA or FYB variant. This gene is present in duplicate (one from the mother and one from the father). If both genes are present in the FYA variant, the phenotype is Fya+ Fyb- or otherwise represented Fy (a+b-). The individual is homozygous for Duffy a. However, if FYA was inherited from the mother and FYB from the father, the phenotype is Fy (a+b+) - heterozygous.

Refractory state - a condition when a patient does not experience a platelet increase after two consecutive platelet transfusions. The cause may be sepsis, increased consumption or, as an immunological cause, antibodies against HLA antigens on the donor platelets. The reason for a refractory state is not always clear-cut.

Serum - when blood plasma clots, the fibrinogen precipitates and what remains is serum.

Stemcells - when we talk about stem cells in a therapeutic sense, we usually mean haematopoietic stem cells. They represent a very early developmental group of blood cells, and their "final destination" has not yet been determined. They can develop into all three cell groups: Erythrocytes, Platelets and Leukocytes. They can be obtained in two different ways: by bone marrow puncture or by apheresis. Both methods have advantages and disadvantages, but apheresis is currently more popular because the cells can be collected from the donor relatively easily.

Thrombozyten - smallest blood cells, are part of the clotting process. They ensure the closure of injuries.
Normal values:
150-400 x 10^3/µl
Transfusion trigger - usually, this means the haemoglobin content of the blood. However, what is becoming increasingly important are the physiological transfusion triggers:
- Compensatory capacity, cardiac and cerebral risk factors.
- Physiological transfusion triggers: e.g. tachycardia, hypotension, ECG ischaemia, lactate acidosis

Wholeblood - the term comes from blood donation. It is blood taken directly from a donor, anticoagulated only, but otherwise not further processed. It is rarely used for direct transfusion because transfusion reactions occur much more frequently. But whole blood is experiencing a renaissance, for example, in war zones.

Last update on 08.08.2023.