Which best explains the difference between immunogens and antigens?

Which best explains the difference between immunogens and antigens?

• A. Only antigens are large enough to be recognized by T cells.
• B. Only immunogens can react with antibody.
• C. Only immunogens can trigger an immune response.
• D. Only antigens are recognized as foreign.

Answer: (C)

The difference hinges on immunogenicity. Immunogenicity is the ability to provoke an immune response. An antigen is any molecule or part that can be recognised by immune receptors, such as antibodies or T cell receptors. Some antigens, like small haptens, can be bound by antibodies but cannot by themselves trigger a full immune response unless they’re attached to a larger carrier. An immunogen, however, has the capacity to be processed and presented by antigen-presenting cells and to stimulate antibody production or T cell activation. That’s why only immunogens can trigger an immune response. For example, a microbial protein is both antigenic and immunogenic, while a hapten alone is antigenic but not immunogenic unless linked to a carrier protein.

The difference hinges on immunogenicity. Immunogenicity is the ability to provoke an immune response. An antigen is any molecule or part that can be recognised by immune receptors, such as antibodies or T cell receptors. Some antigens, like small haptens, can be bound by antibodies but cannot by themselves trigger a full immune response unless they’re attached to a larger carrier. An immunogen, however, has the capacity to be processed and presented by antigen-presenting cells and to stimulate antibody production or T cell activation. That’s why only immunogens can trigger an immune response. For example, a microbial protein is both antigenic and immunogenic, while a hapten alone is antigenic but not immunogenic unless linked to a carrier protein.