Chemotherapy Biotherapy Certification ONS Practice Test 2025 - Free Practice Questions and Study Guide

Molecules that can elicit an immune response are referred to as antigens. Antigens are typically proteins or polysaccharides that reside on the surface of pathogens such as bacteria, viruses, or even cancer cells. When the immune system detects these foreign substances, it activates immune cells that recognize the specific antigen, leading to a cascade of responses aimed at neutralizing or eliminating the threat.

In distinction to other terms, interleukins are a type of cytokine that plays a role in cell signaling within the immune system, and while they are important for immune responses, they do not directly elicit them like antigens do. Antibodies, on the other hand, are produced by B cells in response to antigens; they bind to the antigens to help neutralize them, but they do not themselves elicit an immune response. Enzymes are biological catalysts that facilitate chemical reactions in the body and are not directly involved in the immune response against pathogens. Thus, recognizing antigens as the key players that provoke immune responses is fundamental to understanding immunology.