Which of the following best describes the first line of defense in the innate immune system?

• A. Formation of memory cells for long-term immunity
• B. Activation of B and T lymphocytes to target specific pathogens
• C. Physical and chemical barriers such as skin and mucous membranes
• D. Production of antibodies to neutralize pathogens

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the concept of the innate immune system. The innate immune system is the body's first line of defense against pathogens and is non-specific, meaning it does not target specific pathogens but rather provides a general defense.
2. Step 2: Recognize the components of the first line of defense. These include physical barriers like the skin, which acts as a protective layer, and mucous membranes, which trap and prevent pathogens from entering the body.
3. Step 3: Identify chemical barriers that complement physical barriers. Examples include enzymes in saliva, stomach acid, and antimicrobial peptides that help neutralize or destroy pathogens.
4. Step 4: Compare the first line of defense to other immune responses. Unlike the adaptive immune system, which involves memory cells, B and T lymphocytes, and antibody production, the first line of defense does not involve these specific mechanisms.
5. Step 5: Conclude that the correct description of the first line of defense in the innate immune system is 'Physical and chemical barriers such as skin and mucous membranes,' as these are the primary mechanisms preventing pathogen entry.