RBC (red blood cells) is an important element of blood. There are many antigenic substances present in the surface of RBC. Depending upon the presence or absence of inherited antigenic substances on the surface of RBC, blood may be classified in different groups; these groups are called Blood Group or Blood Type. Other then human, animals and bacteria have cell surface antigens and they have also blood grouping, but their blood groups are quite different.

Human have 29 recognized blood group system (recognized by International Society of Blood Transfusion, ISBT). The popular blood grouping systems are ABO blood group system, Rhesus blood group system, MNS system, Kell system, Lewis system etc. Though ABO blood group system and Rhesus blood group system is most popular in human, but complete blood type would describe a full set of 29 substances on the surface of RBCs.

ABO system, the most important blood group system in human is associated with anti-A antibodies and anti-B antibodies. This group is discovered in 1901. The blood groups of this system are A (genotype AA or AO), B (genotype BB or BO), AB (genotype AB) and O (genotype OO). The second most important blood group system is the Rhesus system. The most significant Rhesus antigen is the RhD antigen. The Rhesus group was discovered in 1937.

There are also different blood groups in non-human. More then 13 canine blood groups and eight Dog Erythrocyte Antigen (DEA) types are recognized as international standards. Recognize system of feline blood designates cats as A, B, or AB. Incase of hours, there are eight recognized blood groups. They are A, C, D, K, P, Q, T, and U. Incase of cattle, the polymorphic systems are A, B, C, F, J, L, M, S, and Z polymorphisms.

There are many clinical significance of blood group like blood transfusion, hemolytic disease of the newborn (HDN) etc. In many countries, blood grouping test is compulsory to get passport, driving license, national ID card etc. In some cases, blood grouping also helps to determine heredity.

My group is O +ve. Iam generally a doner because of my group. Most of the +ve groups are available.

The problem arise with -ve groups.

In biology we looked at a map which gave dominant blood types in each region. It was really interesting to see how different cultures had different predominant blood types. I wonder how this will change over the years as cultures mix more and more.