Foreign instigators are individuals or groups that attempt to influence the internal affairs of a foreign country. They may do this through political, economic, or military means, and their actions can often lead to conflict and instability. Antigens are molecules that are recognized by the immune system as being foreign and can trigger an immune response. Antigens can be found on the surface of bacteria, viruses, and other pathogens, and they are essential for the body's ability to fight off infection.