Distinguish between antigens and antibodies and describe the roles of antibodies.

Antigens and antibodies are both crucial components of the immune system, but they play different roles and have different characteristics.

1. Antigens: These are substances that the immune system recognizes as foreign or potentially harmful. They can be proteins, polysaccharides, or other molecules found on the surfaces of bacteria, viruses, and other pathogens. When an antigen enters the body, it triggers an immune response. The immune system's goal is to eliminate the antigen, either by directly destroying the pathogen it's associated with or by neutralizing the harmful effects of the antigen.

2. Antibodies: These are proteins produced by the immune system in response to an antigen. Each antibody is specific to a particular antigen. When an antibody encounters its corresponding antigen, it binds to it. This binding can neutralize the antigen, making it harmless. Alternatively, the antibody can mark the antigen for destruction by other parts of the immune system.

In summary, antigens trigger an immune response, and antibodies are part of that response. The antibodies' role is to neutralize or mark antigens for destruction, helping to protect the body from infection and disease.