What type of substance causes the body to produce antibodies?

The body produces antibodies in response to antigens, which are substances that the immune system recognizes as foreign or harmful. Antigens can be components of pathogens like bacteria and viruses, or they can be found in other substances that enter the body, such as allergens or toxins. When the immune system detects an antigen, it triggers a response that includes the production of antibodies specifically designed to bind to that antigen. This binding can neutralize the threat or mark it for destruction by other components of the immune system. Therefore, antigens play a crucial role in activating the immune response and promoting antibody formation.