The immune system comprises a network of cells, tissues and organs that work together to defend the body against the attack of foreign pathogens.
When antigens (foreign substances that invade the body) are detected, several types of cells work together to recognize them and respond. These cells are called antibodies. These are specialized proteins that lock onto specific antigens. Once produced, these antibodies continue to exist in a person's body, so that if the same antigen is presented to the immune system again, the antibodies are already there to do their job.