Blood is an essential life-maintaining fluid that circulates throughout our entire body. There are three main categories of blood cells: red blood cells, white blood cells and platelets. Every blood cell begins life as an unspecialized cell called a stem cell. Stem cells eventually mature to fall into one of the aforementioned three main categories. It's important to note that each cell in our body has a limited lifespan and must be replaced constantly.
What are red blood cells?
Red blood cells, or erythrocytes, give blood its distinctive color and make up about 40-45% of blood's volume. Red blood cells are produced in our bone marrow where they typically live for about 120 days. The red blood cell's main function is to carry oxygen from the lungs and deliver it throughout our body. Red blood cells also transport waste such as carbon dioxide back to our lungs to be exhaled. Red blood cells can carry oxygen due to a protein called hemoglobin. Hemoglobin is made of two main parts: the "heme" group and the "globin" group. The heme group contains iron which gives the red color to the red blood cell. The globin group is a protein that helps the red blood cell carry and hold oxygen in place as it moves throughout the body.
How are red blood cells used?
Certain conditions within our bodies may trigger the production of red blood cells. For example, if our body doesn't have enough blood cells or our body tissue lacks oxygen. Then a hormone called erythropoietin will stimulate the bone marrow to produce more red blood cells.
However, there are instances where our body cannot produce enough red blood cells to meet the demand our body needs. If the number of blood cells is too low, this is known as anemia. When a person is anemic, their blood carries less oxygen throughout the body, which may result in fatigue and weakness. Having a low number of red blood cells could be a result of trauma, surgery, blood loss or blood disorders such as sickle cell disease.
Red blood cell donations are important to help patients who cannot produce enough red blood cells. The Red Cross calls red blood cell donations "Power Red" donations. By donating Power Reds, you double your impact by contributing two units of red blood cells in just one donation.
What are white blood cells?
White blood cells, or leukocytes, are part of the body's immune system, where there is one white blood cell for every 600 to 700 red blood cells. The white blood cell's main function is to help fight infections. Most of our white blood cells are individualized to our specific bodies, which is why white blood cells are removed from transfusable blood. Removing the white blood cells from transfusable blood is known as leuko-reduction, which prevents the blood from causing a negative reaction during donation.
There are five main types of white blood cells:
Lymphocytes: Help the body make cells that fight against infection and make antibodies.
Monocytes: Help other white blood cells to remove damaged tissue and gobble up bacteria, viruses, debris and infectious organisms.
Eosinophils: Kill parasites, destroy cancer cells and help the immune system with an allergic response.
Basophils: Release histamine if there is an allergic reaction; help prevent blood clots.
Neutrophils: Help heal damaged tissue and resolve an infection.
How are White Blood Cells Used?
The list of white blood cells mentioned is broken up into two categories: granulocytes and agranulocytes. The agranulocytes are the lymphocytes and monocytes. The granulocytes include eosinophils, basophils and neutrophils.
Currently, the Red Cross collects granulocytes to help treat infections that don't respond to antibiotics. This process is known as apheresis and the cells must be transfused to the patient within 24 hours of donation. Donated granulocytes are collected on an as-needed basis. To be eligible to donate granulocytes, you must have donated platelets through the Red Cross within the past 30 days.
What are platelets?
Platelets, or thrombocytes, are tiny blood cells that can only be seen under a microscope. They are made from the spongy center inside our bones known as bone marrow. Platelets typically live for about 8 to 10 days in our body. A platelet's main function is to rush to an injury in the blood vessel and form a plug to fix the damage. This plug is known as a clot, or thrombus, which helps prevent blood loss.
However, there are conditions where the body may produce too little or too many platelets. Too many platelets are known as thrombocythemia, where there is excessive clotting. When there are too few platelets in the blood this is known as thrombocytopenia, where bruising and abnormal bleeding become more likely.
How Are Platelets Used?
Because platelets help control bleeding, they are mainly used for cancer treatments, organ transplants, surgeries, and platelet dysfunctions. Platelets can be extracted from a whole blood donation using a centrifuge or they can be collected using an automated process. This process allows, one donor to contribute four to six times as many platelets as platelets collected from a whole blood donation. And because platelets need to be used within five days of donation, there is a constant need for platelet donors!