Blood is composed of cells bathed in a fluid matrix called plasma. The cells constitute 45% by volume of the blood while the other 55% is represented by the plasma. The human blood is divided into 4 types A, B, AB and O. Whether a person has A,B,AB or O blood group is determined by a short chain of sugars covalently bonded to membrane lipids and proteins of the RBC. A person with blood type AB has gangliosides with both A and B structures. The ABO determinants are short , branched oligosaccharide chains. Along with this rhe red cells of 85% population contains rehsus factor and are called rehsus positive or RH + and those who do not have it are called as rehsus negative or RH -VE.
Blood Group A
In blood two agglutinogens exits which act as antigens and react with antibodies in the plasma. They are A and B respectively. The complimentary plasma agglutinins are named a and b. A person with specific agglutinogens in the red cells does not possess the corresponding agglutinin a in the plasma. Hence a person with agglutinigen A in the red cell membrane has no agglutinin a in the plasma and is classified under blood group A. Based on the presence of rehsus factor it can be further classified as A+VE or A-VE blood types.
Blood Group B
The red blood cells which contain only B agglutinogens and does not contain corresponding agglutinin b in the plasma are classified as blood group B. Based on the presence of rhesus factor it is further classified into B+VE and B -VE. The persons who have rehsus factor on their red blood cells membrane along with agglutinogen B are called as B+Ve whereas the ones who do not have rehsus factor on their membrane are classified as B-VE blood type.
Blood Group AB
The red blood cells which contain both A and B agglutinogens and does not contain corresponding agglutinin a and b in the plasma are classified as blood group AB. Based on the presence of rhesus factor it is further classified into AB+VE and AB-VE. The people with AB blood group are called as universal recipient however they can donate only to AB blood types.
Blood Group O
The red blood cells does not contain both A and B agglutinogens and does not contain corresponding agglutinin a and b in the plasma are classified as blood group O. Based on the presence of rhesus factor it is further classified into O+VE and O-VE. The people with O blood group are called as universal donor.
Blood group determination is very important especially in the case of blood transfusion. When a patient receives blood transfusion it is imperative that he receives blood that is compatible with his own else it results in agglutination which can be fatal.