Blood, Types and ABO Testing

A Knowledge Base Article from Medika Life

Your blood is made up of liquid and solids. The liquid part, called plasma, is made of water, salts, and protein. Over half of your blood is plasma. The solid part of your blood contains red blood cells, white blood cells, and platelets.

Red Blood Cells

Red blood cells (RBC) are also called erythrocytes. They deliver oxygen from your lungs to your tissues and organs. Blood cells constantly die and your body makes new ones. Red blood cells live about 120 days. Red blood cells are the most common type of blood cell and your principal means of delivering oxygen to the body tissues—via blood flow through the circulatory system.

The cytoplasm of erythrocytes is rich in hemoglobin, an iron-containing biomolecule that can bind oxygen and is responsible for the red color of the cells. Carbon monoxide is so dangerous because it binds far better to hemoglobin than oxygen.

White Blood Cells

White blood cells (WBCs), also called leukocytes or leucocytes. They are a component of the immune system that is involved in protecting the body against both infectious disease and foreign invaders. All white blood cells are produced and derived from cells in the bone marrow known as hematopoietic stem cells. Leukocytes are found throughout the body, including the blood and lymphatic system. Some white blood cells live less than a day, but others live much longer.

All white blood cells have nuclei, which distinguishes them from the other blood cells, such as red blood cells and platelets. The two main categories of white blood cells are granulocytes and agranulocytes.


Platelets, also called thrombocytes, help blood to clot when you have a cut or wound. Bone marrow, the spongy material inside your bones, makes new blood cells. and platelets live about 6 days. Like red cells, platelets have no nucleus. However, unlike red cells that originate in the marrow as nucleated cells and lose their nucleus, platelets are produced by budding off from a giant multi nucleated marrow cell called a megakaryocyte.

Facility at The National Cancer Institute at Frederick (NCI-Frederick)– Red blood cell (red), Platelet (yellow), white blood cell (blue)–From left to right: erythrocyte, thrombocyte, leukocyte

Blood Plasma

Blood plasma is the pale yellow colored liquid component of blood that normally holds the blood cells in whole blood in suspension. It makes up about 55% of the body’s total blood volume. It is the intravascular fluid part of extracellular fluid (all body fluid outside of cells).

It is mostly water (up to 95% by volume), and contains dissolved proteins (6–8%) (i.e.—serum albumins, globulins, and fibrinogen), glucose, clotting factors, electrolytes (Na+, Ca2+, Mg2+, HCO3−, Cl−, etc.), hormones, and carbon dioxide . Plasma also serves as the protein reserve of the human body. It plays a vital role in an intravascular osmotic effect that keeps electrolytes in balanced form and protects the body from infection and other blood disorders.

How Blood is Typed (classified)

Blood types are determined by the presence or absence of certain antigens – substances that can trigger an immune response if they are foreign to the body.  Since some antigens can trigger a patient’s immune system to attack the transfused blood, safe blood transfusions depend on careful blood typing and crossmatching.

There are four major blood groups determined by the presence or absence of two antigens – A and B – on the surface of red blood cells. In addition to the A and B antigens, there is a protein called the Rh factor, which can be either present (+) or absent (–), creating the 8 most common blood types (A+, A-, B+, B-, O+, O-, AB+, AB-).

We use one of two systems to classify blood, the ABO system or the Rh System. The Rh System simply classifies you as being Rh+ or Rh-. Being positive means simply your blood has the Rh protein antigen, being negative indicates the protein antigen is not present in your blood. The ABO system identifies the presence, or absence, of A,B, AB antigens in your blood

  • Donors with blood type A… can donate to recipients with blood types A and AB
  • Donors with blood type B… can donate to recipients with blood types B and AB
  • Donors with blood type AB… can donate to recipients with blood type AB only
  • Donors with blood type O… can donate to recipients with blood types A, B, AB and O (O is the universal donor: donors with O blood are compatible with any other blood type)

Rh-negative blood is given to Rh-negative patients, and Rh-positive or Rh-negative blood may be given to Rh-positive patients. The rules for plasma are the reverse. Things become more complicated with the addition of the Rh Factor protein. the info-graphic provided below expands the full combinations of the donor/ recipient relationship.

Note: The universal red cell donor has Type O negative blood.The universal plasma donor has Type AB blood.

Image courtesy of Creative Commons License. Click to enlarge

Prevalence of Blood Types Globally

Just how widespread are certain blood types within the general population? AB- is by far the rarest. Refer to the info-graphic below for other blood types.

Image courtesy of Creative Commons License. Click to enlarge

Inheriting Blood Types

Like eye color, blood type is passed genetically from your parents. Whether your blood group is type A, B, AB or O is based on the blood types of your mother and father. This makes blood typing an integral part of paternity suits. The table below will explain the combinations in more detail.

Imagecourtesy of

Note: If you have questions about paternity testing or about blood group inheritance, your primary care physician should be able to provide you with an appropriate referral. Testing difficulties can cause exceptions to the above patterns. ABO blood typing is not sufficient to prove or disprove paternity or maternity.


Medika Life has provided this material for your information. It is not intended to substitute for the medical expertise and advice of your health care provider(s). We encourage you to discuss any decisions about treatment or care with your health care provider. The mention of any product, service, or therapy is not an endorsement by Medika Life

Medika Life
Medika Life
Medika Life is a digital Health Publication for both the medical profession and the public. Make informed decisions about your health and stay up to date with the latest developments and technological advances in the fields of medicine.
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