Why do we have blood types?

Blood is bodily fluid that circulates through body and deliver essential nutrients and oxygen to every cell of our body.

For thousands of years nobody really understood blood. A greek doctor from 200 BC believed that blood was created from food and liver, this thought lived nearly 1500 years. It was early 17th century when a British ‘Dr. William Harvey’ discovered that blood circulated circulated through body. This experiment spawned the age of blood transfusion. In 1665 an english physician successfully kept one dog alive by transfusing blood of another dog into his body. Later after two years doctors experimented transfusing animals blood into human body in which the human patient died due to blood clotting.

It wasn’t until 1900s when ‘Dr. Karl Landsteiner’ understood that animals even humans have different blood. He later researched on blood and developed a system to categorize blood type known as A-B-O blood group system. Dr. Landsteiner traced transfusion complication like death and blood clot is caused by two things Antigens and Antibodies. Antigen is anything that triggers our immune system to respond. Usually viruses and Bacteria fall in this category, usually our immune system recognize these invaders and deploy antibodies to destroy them. Antibodies are proteins produced by our immune system that can recognize, investigate and if needed can destroy Antigens.But our own body also produce some Antigens called Self-Antigens which our immune system leave them alone. The whole A-B-O group system  is based upon these sugar based Self-Antigens and corresponding protein based antibodies. 

Depending upon the presence and absence of these Antigens and Antibodies our blood is divided into four types. Type A blood has A-antigen on blood and B-antibody in plasma. Type B blood has B-antigen on blood and A-antibody in plasma. Type AB has both A-antigen and B-antigen with no Antibodies in plasma. Type O has both A-antibody and B-antibody with no Antigens on blood. 

The positives and the negatives after our blood type is given by detecting the presence or absence of Rh protein based Antigen. Presence of Rh protein gives positive sign after blood type while absence gives negative sign after blood type. 

Blood is foremost the most important fluid in our body. By understanding our blood we can ensure tranfusing right blood type to the needy ones.