Any substance that causes the production of antibodies by the body's immune system. Common antigens include the proteins carried on the surface of bacteria, viruses, and pollen grains. The proteins of incompatible blood groups or tissues also act as antigens, which has to be taken into account in medical procedures such as blood transfusions and organ transplants.
Yellow represents the golden land of South America. Blue stands for the ocean separating the country from Spain. Red symbolizes the blood and courage of the people resisting the tyrants. Effective date: 26 November 1861.