Microbiology Practice Exam 2025 – 400 Free Practice Questions to Pass the Exam

The second line of defense in the immune system involves mechanisms that provide a more immediate and nonspecific response to pathogens that have breached the first line of defense, which consists mainly of physical barriers like skin and mucous membranes.

The correct answer focuses on components such as white blood cells, antimicrobial proteins, and the inflammatory response. White blood cells, such as phagocytes, play a crucial role in identifying and eliminating pathogens that enter the body. Antimicrobial proteins, including complement proteins and interferons, help to destroy invaders and inhibit their spread. The inflammatory response is a critical process that involves various signaling molecules and cells, leading to increased blood flow and immune cell recruitment to the site of infection or injury, which enhances the body’s ability to combat threats.

This contrasts with the first line of defense, comprised of the skin and mucous membranes, which physically block pathogens from entering the body. The option mentioning lymphocytes and antibodies pertains more to the third line of defense, which is characterized by a specific immune response involving adaptive immunity. Neural pathways, while important for overall bodily function and response to stimuli, are not considered a direct part of the immune defense mechanisms in this context.