Types of white blood cells

A straw-coloured liquid containing suspended white blood cells. Is around 90% water, including electrolytes (ie; sodium, potassium, proteins). Also known as erythrocytes, red blood cells are essentially only used to carry oxygen around the blood. Red blood cells contain the protein, haemoglobin, which combines with oxygen to form Oxyhaemoglobin. Red blood cells are produced in the bone marrow, and are typically 6–8 μm, with million per micro-litre of blood. There are numerous types of white blood cells(also known as leucocytes), though they all share the same function – they help fight off diseases and infections. They are on average, 15 μm, only live for a few days (some even only a few hours!), and there are roughly 5-10 thousand per micro-litre of blood. Also referred to as thrombocytes, platelets are cell fragments which are disc shaped which help clot the blood from cuts to prevent excess loss of body fluids.

There are three main types of blood donation; 1.Homologous: A standard whole blood donation, consisting of plasma, red and white blood cells, platelets, antibodies and other components. 2.Plasma donation: Plasma is separated from the other components by a special machine (centrifuge), then the red blood cells are returned to the donor in cycles throughout the donation, this method is also known as apheresis. 3.Platelet donation: This procedure is known as plateletpheresis and works similarly to the apheresis process, which returns both the red cells and plasma to the donor. Donated blood is separated by a process called centrifugation. A centrifuge is an electrically driven motor which spins the blood around separating it into its different parts. The heavier parts (ie; red blood cells) go to the outside, the platelet's stay roughly in the middle, and the light blood plasma stays on the top.

Blood is placed into the centrifuge¹ and separates into plasma², leukocytes³, and erythrocytes⁴ the selected components are then drawn off⁵. An example of apheresis.

Blood can be used immediately once donated, it can be used as whole blood or it can be separated into its components. Whole blood is given to patients where major functions of the blood (such as oxygen carrying capacity) are damaged, or where at least 20% of blood has been lost and there is a decrease in blood pressure. Three of the main blood products extracted from donated blood are red blood cells (RBCs), platelet concentrate, and fresh frozen plasma (FFP): RBCs help patients who aren't capable of carrying enough oxygen. RBC’s may also be used to help replace cells lost from significant bleeding, as the result of an accident. Platelets are essential for the coagulation (clotting) of blood and are used to treat bleeding caused by conditions or diseases where platelets aren’t able to function properly. FFP is used mostly to provide blood components that coagulate blood.FFP contains all coagulation factors in normal amounts and is free from other blood components (red blood cells, white blood cells and platelets). It’s used for patients who require immediate clotting effects, such as those who have had their blood thinned or when huge transfusions have taken place.

A blood substitute (also known as artificial blood) is any substance which that can copy and fulfil some of the functions of real blood. Though true blood serves many different functions, artificial blood is designed for the main purpose of transporting oxygen and carbon dioxide around the body. Variant on the type of artificial blood, it can be produced in multiple ways using synthetic production, chemical isolation, or recombinant biochemical technology. Development of the first artificial blood goes back to the early 1600s, and the search for the ideal blood substitute continues. Many manufacturers have products in clinical trials, some of which are not safe for use.

Scientists originally wanted a substitute for blood as they believed a disease was caused by bad blood. However, later on physicians discovered the need for blood transfusions after such events resulting in great blood loss such as childbirth, and war trauma. Recently, the AIDS epidemic has not only lessened the public’s confidence in blood banks, the high cost of viral screening has also caused financial stress. As a result of this epidemic, blood transfusion techniques were carefully reviewed to try reduce the amounts of blood administered, not only to rising risks and costs, but also to shortages in blood banks. The transfusion trigger, or the critical point at which a physician decides to transfuse a patient, has been changed in recent years. Adverse reactions occur in 20% of all transfusions. As the need for more blood increases (such as more trauma patients) the risk greatly increases as more people donate, and the possibility of cross-match error also increases. During storage, the physiological characteristics of blood can alter, and the longer blood is stored the more dangerous these changes can be. The pH of blood decreases over time, and could cause acidosis in a patient. The main goal of any transfusion is to create a system with no side effects or extra medical care. Technologies of the future hope to generate the perfect blood substitute, which will surely have an impact on transfusion medicine and services. Sweden has already tested artificial blood on eight patients with no side effects. Currently the prospect of using artificial blood is difficult to foresee owing to problems as mentioned above but also of the short half lives, prolonged tissue retention, potential toxicity and the issues of cost, availability of raw materials and strict laws including ethical issues.

– Australian Red Cross, 11/11/ – Australia Red Cross Blood Service, 17/11/ ion?OpenDocument – Consulted and approved by Australian Red Cross Blood Service, 11/11/12 ion?OpenDocument – Community Blood Center, 17/11/ – Indian Journal of Critical Care Medicine, 18/11/ – iStudy Australia, 11/11/ National Blood Authority Australia, 18/11/ NHS, 11/11/ NSW HSC, 17/11/ Sara J Grethlein, 11/11/ Sporty Injury Clinic, 18/11/ Suman Sarkar, 17/11/ /11/12