NLN Science Practice Exam 2025 – Complete Prep Guide

Vaccines primarily stimulate the immune system by exposing it to antigens. An antigen is any substance that can provoke an immune response, typically derived from a pathogen such as a virus or bacteria. When a vaccine is administered, it introduces a harmless form of the pathogen or a piece of it, such as proteins or sugars, which is recognized as foreign by the immune system.

This exposure prompts the immune system to produce specific antibodies and activate T-cells tailored to respond to the pathogen. The immune system forms a memory of these antigens, leading to a quicker and more robust response upon future encounters with the actual pathogen. This process is fundamental to how vaccines work, as they train the immune system to recognize and fight off infections without causing the disease itself.

In contrast, the other options do not directly relate to the mechanism by which vaccines operate. Raising blood pressure, increasing body temperature, and producing hormones do not contribute to the primary function of vaccines in stimulating the immune response through antigen recognition and memory formation.