Which of the following is a cellular component of the innate immune defenses?

• A. B lymphocytes
• B. Plasma cells
• C. Macrophages
• D. Cytotoxic T cells

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the innate immune system. The innate immune system is the body's first line of defense against pathogens. It is non-specific and responds quickly to infections, unlike the adaptive immune system, which is specific and slower to respond.
2. Step 2: Identify the cellular components of the innate immune system. These include macrophages, neutrophils, dendritic cells, natural killer (NK) cells, and mast cells. These cells are responsible for recognizing and eliminating pathogens without prior exposure.
3. Step 3: Differentiate between innate and adaptive immune cells. B lymphocytes, plasma cells, and cytotoxic T cells are part of the adaptive immune system, which requires activation and is specific to particular antigens. Macrophages, on the other hand, are part of the innate immune system and act as phagocytes to engulf and destroy pathogens.
4. Step 4: Focus on macrophages. Macrophages are key players in the innate immune system. They are derived from monocytes and are responsible for phagocytosis, antigen presentation, and releasing cytokines to recruit other immune cells.
5. Step 5: Conclude that macrophages are the correct answer. Based on the distinction between innate and adaptive immune cells, macrophages are the cellular component of the innate immune defenses listed in the options.