Antigens are proteins which our immune system can recognise. Any antigen that is ‘foreign’ to our immune system is destroyed by an antibody. Majority of antigens are proteins but some are carbohydrates, lipids, and nucleic acids.
Antibodies are attack molecules our immune system makes to protect ourselves against foreign things such as bacteria and viruses.
Antibodies circulate throughout the body until they find and attach to the antigen. Once attached, they can force other parts of the immune system to destroy the cells containing the antigen.
Whenever we refer a pathogen (disease causing organisms), we may think the entire microbe is responsible for the disease.
But the fact is these organisms possess numerous sites called as epitopes that are recognized by antibodies or receptors on the cells in the immune system.