What Are the Different Blood Types?

Have you ever wondered what exactly makes A-positive blood different from O-negative blood? Here is a quick tutorial from your trusted home care agency on blood types.

All blood contains the same elements, but not all blood is the same. Human blood has red blood cells to carry oxygen. Plasma is the watery stuff that allows blood to flow. Blood also contains antigens that alert the immune system to possible foreign invaders, such as viruses or bacteria. These antigens can be seen on the red blood cell surfaces, in the plasma, in both or in neither. Scientists categorize blood into eight different categories, based on the presence or absence of antigens in the blood.

Blood Group Systems

Scientists look for two antigens on red cells and in plasma when determining blood type: antigen A and antigen B.

There are four groups of blood: A, B, AB, and O. People with group A blood contain an A antigen on red blood cells and the B antigen in plasma. Those with group B blood contain a B antigen on red blood cells and the A antigen in plasma. AB means the red cell contains both antigens A and B but contains neither one in plasma. Finally, blood type O means there is neither A nor B antigen on the red cells but the plasma contains both.

Positive and Negative

Scientists further categorize blood types according to the absence or presence of a third type of antigen known as the rH factor. When a patient has type A blood and rH antigen, a medical professional will say the patient has A-positive blood. Someone with type O blood and no rH has type O-negative blood.