Red blood cells (erythrocytes) are the most cells (leukocytes) are an important part of your immune system and platelets are cell fragments that aid in blood clotting when a blood vessel is injured. Plasma is the fluid part of the blood; it consists mainly of water, but also salts and proteins that maintain osmotic balance, buffer changes in pH and transport materials. Although all humans have these same components, there are 4 different blood groups inherited in a co-dominance pattern. These phenotypes are A, B, O and AB as you read earlier. Blood groups result from the presence of complex carbohydrates called antigens; A and/or B on the surface of red blood cells. An individual who is blood group 'A' has only A antigens on the surface of their red blood cells. An individual who is blood group 'B' has only B antigens, and an individual who is blood group 'AB' has both (co-dominance). Individuals with the 'O' blood group have neither A or B antigens.
Group A
Group B
Group AB
Group O
Surface antigen A
Surface antigen B
Surface antigens A and B
Neither A nor B surface antigens
Another antigen, a protein called the Rh factor, is either present or absent on the surface of blood cells. Individuals with blood possessing the Rh antigen are Rh positive (+), individuals who lack the antigen are Rh negative (-). Therefore, individuals are said to be A+, A-, B+, B-, O+, O-, AB+ or AB- depending on which antigens are found on their red blood cells' surface.
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