OSMT (Ontario Society of Medical Technologists) Practice Exam

A hapten is:

1. a. a tiny cell

2. b. incomplete antigen

3. c. self-protein

4. d. all of the above

The correct answer is: b. incomplete antigen

A hapten is indeed best described as an incomplete antigen. Haptens are small molecules that, by themselves, do not elicit an immune response. They can bind to larger carrier proteins, and this complex can then trigger an immune response. This is critical in immunology because it highlights the distinction between full antigens, which can provoke an immune response on their own, and haptens, which require the presence of a carrier to be recognized by the immune system. The other options provided do not accurately describe haptens. For instance, a "tiny cell" does not accurately capture the nature of haptens, as haptens refer to non-cellular small molecules rather than cellular entities. Similarly, "self-protein" refers to proteins that originate from the host organism and are typically recognized by the immune system as self, rather than foreign. Thus, the correct understanding of a hapten focuses on its role as an incomplete antigen that needs a carrier for immune recognition.