What is capable of eliciting an immune response?

The most appropriate answer is immunogen. An immunogen is a substance that is capable of provoking an immune response when introduced into the body. Immunogens can be large molecules, such as proteins, polysaccharides, or nucleic acids, and they stimulate the production of antibodies or activate T-cells as part of the adaptive immune response.

While the terms antigen and pathogen might seem related, they do not fully capture the essence of the question. An antigen is any molecule that can bind to an antibody or a receptor on a T cell, which may include those that are not necessarily capable of eliciting a full immune response on their own. For example, a small peptide might be antigenic but not sufficiently large or complex to function as an immunogen without additional factors.

Pathogens, which include bacteria, viruses, fungi, and other microorganisms, can indeed trigger an immune response because they are often composed of various immunogenic structures. However, not every pathogen is inherently immunogenic in the context of triggering a robust immune response, especially if they have evolved mechanisms to evade detection.

Seroantigen refers specifically to antigens that react with specific antibodies in serum, which implies a more narrow context rather than a broader definition that encompasses everything capable of elic