What are antibodies?

Antibodies are specialized proteins secreted by white blood cells, specifically B cells, in response to the presence of foreign substances known as antigens. These antigens can be pathogens such as bacteria or viruses, or they can be other foreign molecules. The primary function of antibodies is to attach to these specific antigens in order to neutralize them or mark them for destruction by other components of the immune system. This interaction is crucial for the body’s defense mechanism against infections and in the immune response.

The other choices do not accurately describe antibodies. For instance, while platelets do play a vital role in blood clotting, they do not produce antibodies; instead, they are involved primarily in hemostasis. Salts regulating bodily fluids describe electrolytes and their functions rather than antibodies, which are immune proteins. Lastly, cells responsible for creating blood clots refer to platelets and certain other blood cells, not antibodies. Therefore, the identification of antibodies as proteins secreted by white blood cells that attach to specific antigens directly aligns with their biological roles in the immune system.